Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$243.37	13.294%	$275.7236	$275.72	$275.70	$275.70
Purchase #2	$113.58	12.559%	$127.8445	$127.84	$127.85	$127.80
Purchase #3	$187.56	5.737%	$198.3203	$198.32	$198.30	$198.30
Purchase #4	$160.69	12.779%	$181.2246	$181.22	$181.20	$181.20
Purchase #5	$115.65	12.694%	$130.3306	$130.33	$130.35	$130.30
Purchase #6	$124.42	13.355%	$141.0363	$141.04	$141.05	$141.00
Purchase #7	$141.33	13.257%	$160.0661	$160.07	$160.05	$160.10
7 purchase totals =	$1,086.60		$1,214.5460	$1,214.54	$1,214.50	$1,214.40