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	$91.49	11.564%	$102.0699	$102.07	$102.05	$102.10
Purchase #2	$37.60	5.549%	$39.6864	$39.69	$39.70	$39.70
Purchase #3	$197.30	3.711%	$204.6218	$204.62	$204.60	$204.60
Purchase #4	$81.93	9.401%	$89.6322	$89.63	$89.65	$89.60
Purchase #5	$184.78	6.343%	$196.5006	$196.50	$196.50	$196.50
Purchase #6	$175.68	7.334%	$188.5644	$188.56	$188.55	$188.60
Purchase #7	$64.84	10.157%	$71.4258	$71.43	$71.45	$71.40
7 purchase totals =	$833.62		$892.5011	$892.50	$892.50	$892.50