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	$162.92	3.294%	$168.2866	$168.29	$168.30	$168.30
Purchase #2	$96.68	7.409%	$103.843	$103.84	$103.85	$103.80
Purchase #3	$232.34	7.829%	$250.5299	$250.53	$250.55	$250.50
Purchase #4	$143.89	3.518%	$148.9521	$148.95	$148.95	$149.00
Purchase #5	$223.65	10.503%	$247.14	$247.14	$247.15	$247.10
Purchase #6	$174.55	12.494%	$196.3583	$196.36	$196.35	$196.40
Purchase #7	$162.49	10.530%	$179.6002	$179.60	$179.60	$179.60
7 purchase totals =	$1,196.52		$1,294.7101	$1,294.71	$1,294.75	$1,294.70