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	$149.56	3.281%	$154.4671	$154.47	$154.45	$154.50
Purchase #2	$208.59	6.331%	$221.7958	$221.80	$221.80	$221.80
Purchase #3	$214.97	11.377%	$239.4271	$239.43	$239.45	$239.40
Purchase #4	$191.59	3.795%	$198.8608	$198.86	$198.85	$198.90
Purchase #5	$39.32	8.173%	$42.5336	$42.53	$42.55	$42.50
Purchase #6	$170.46	8.606%	$185.1298	$185.13	$185.15	$185.10
Purchase #7	$235.45	8.805%	$256.1814	$256.18	$256.20	$256.20
7 purchase totals =	$1,209.94		$1,298.3956	$1,298.40	$1,298.45	$1,298.40