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	$100.29	11.224%	$111.5465	$111.55	$111.55	$111.50
Purchase #2	$143.31	7.414%	$153.935	$153.94	$153.95	$153.90
Purchase #3	$231.50	13.418%	$262.5627	$262.56	$262.55	$262.60
Purchase #4	$32.47	4.222%	$33.8409	$33.84	$33.85	$33.80
Purchase #5	$49.45	12.679%	$55.7198	$55.72	$55.70	$55.70
Purchase #6	$126.57	12.825%	$142.8026	$142.80	$142.80	$142.80
Purchase #7	$98.74	13.317%	$111.8892	$111.89	$111.90	$111.90
7 purchase totals =	$782.33		$872.2967	$872.30	$872.30	$872.20