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	$187.81	6.186%	$199.4279	$199.43	$199.45	$199.40
Purchase #2	$16.64	3.675%	$17.2515	$17.25	$17.25	$17.30
Purchase #3	$232.48	8.229%	$251.6108	$251.61	$251.60	$251.60
Purchase #4	$26.90	7.220%	$28.8422	$28.84	$28.85	$28.80
Purchase #5	$199.67	9.561%	$218.7604	$218.76	$218.75	$218.80
Purchase #6	$105.90	5.317%	$111.5307	$111.53	$111.55	$111.50
Purchase #7	$59.32	13.612%	$67.3946	$67.39	$67.40	$67.40
7 purchase totals =	$828.72		$894.8181	$894.81	$894.85	$894.80