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	$64.46	12.811%	$72.718	$72.72	$72.70	$72.70
Purchase #2	$134.75	10.534%	$148.9446	$148.94	$148.95	$148.90
Purchase #3	$155.75	10.118%	$171.5088	$171.51	$171.50	$171.50
Purchase #4	$73.27	7.523%	$78.7821	$78.78	$78.80	$78.80
Purchase #5	$214.68	10.240%	$236.6632	$236.66	$236.65	$236.70
Purchase #6	$229.27	11.447%	$255.5145	$255.51	$255.50	$255.50
Purchase #7	$70.77	3.846%	$73.4918	$73.49	$73.50	$73.50
7 purchase totals =	$942.95		$1,037.6230	$1,037.61	$1,037.60	$1,037.60