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	$146.82	8.368%	$159.1059	$159.11	$159.10	$159.10
Purchase #2	$28.51	8.576%	$30.955	$30.96	$30.95	$31.00
Purchase #3	$162.75	12.162%	$182.5437	$182.54	$182.55	$182.50
Purchase #4	$229.48	11.760%	$256.4668	$256.47	$256.45	$256.50
Purchase #5	$110.79	7.827%	$119.4615	$119.46	$119.45	$119.50
Purchase #6	$155.56	11.390%	$173.2783	$173.28	$173.30	$173.30
Purchase #7	$167.69	13.851%	$190.9167	$190.92	$190.90	$190.90
7 purchase totals =	$1,001.60		$1,112.7279	$1,112.74	$1,112.70	$1,112.80