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	$100.97	10.820%	$111.895	$111.90	$111.90	$111.90
Purchase #2	$177.40	4.818%	$185.9471	$185.95	$185.95	$185.90
Purchase #3	$214.81	7.792%	$231.548	$231.55	$231.55	$231.50
Purchase #4	$60.93	5.482%	$64.2702	$64.27	$64.25	$64.30
Purchase #5	$187.82	10.142%	$206.8687	$206.87	$206.85	$206.90
Purchase #6	$220.43	5.124%	$231.7248	$231.72	$231.70	$231.70
Purchase #7	$215.37	4.217%	$224.4522	$224.45	$224.45	$224.50
7 purchase totals =	$1,177.73		$1,256.7060	$1,256.71	$1,256.65	$1,256.70