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	$83.37	11.502%	$92.9592	$92.96	$92.95	$93.00
Purchase #2	$216.81	8.114%	$234.402	$234.40	$234.40	$234.40
Purchase #3	$236.82	3.215%	$244.4338	$244.43	$244.45	$244.40
Purchase #4	$106.52	4.810%	$111.6436	$111.64	$111.65	$111.60
Purchase #5	$124.94	6.738%	$133.3585	$133.36	$133.35	$133.40
Purchase #6	$229.54	9.212%	$250.6852	$250.69	$250.70	$250.70
Purchase #7	$94.31	12.277%	$105.8884	$105.89	$105.90	$105.90
7 purchase totals =	$1,092.31		$1,173.3707	$1,173.37	$1,173.40	$1,173.40