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	$81.59	12.625%	$91.8907	$91.89	$91.90	$91.90
Purchase #2	$156.94	6.776%	$167.5743	$167.57	$167.55	$167.60
Purchase #3	$199.37	9.131%	$217.5745	$217.57	$217.55	$217.60
Purchase #4	$94.82	6.844%	$101.3095	$101.31	$101.30	$101.30
Purchase #5	$235.77	4.818%	$247.1294	$247.13	$247.15	$247.10
Purchase #6	$88.43	13.598%	$100.4547	$100.45	$100.45	$100.50
Purchase #7	$99.82	13.536%	$113.3316	$113.33	$113.35	$113.30
7 purchase totals =	$956.74		$1,039.2647	$1,039.25	$1,039.25	$1,039.30