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	$131.84	11.618%	$147.1572	$147.16	$147.15	$147.20
Purchase #2	$123.31	10.380%	$136.1096	$136.11	$136.10	$136.10
Purchase #3	$226.53	11.779%	$253.213	$253.21	$253.20	$253.20
Purchase #4	$148.73	5.180%	$156.4342	$156.43	$156.45	$156.40
Purchase #5	$121.64	5.613%	$128.4677	$128.47	$128.45	$128.50
Purchase #6	$108.55	13.703%	$123.4246	$123.42	$123.40	$123.40
Purchase #7	$80.90	13.362%	$91.7099	$91.71	$91.70	$91.70
7 purchase totals =	$941.50		$1,036.5162	$1,036.51	$1,036.45	$1,036.50