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	$120.29	8.435%	$130.4365	$130.44	$130.45	$130.40
Purchase #2	$183.79	8.549%	$199.5022	$199.50	$199.50	$199.50
Purchase #3	$173.89	13.141%	$196.7409	$196.74	$196.75	$196.70
Purchase #4	$119.93	6.360%	$127.5575	$127.56	$127.55	$127.60
Purchase #5	$118.56	6.740%	$126.5509	$126.55	$126.55	$126.60
Purchase #6	$53.43	9.136%	$58.3114	$58.31	$58.30	$58.30
Purchase #7	$171.62	8.366%	$185.9777	$185.98	$186.00	$186.00
7 purchase totals =	$941.51		$1,025.0771	$1,025.08	$1,025.10	$1,025.10