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	$70.25	7.213%	$75.3171	$75.32	$75.30	$75.30
Purchase #2	$83.73	12.332%	$94.0556	$94.06	$94.05	$94.10
Purchase #3	$98.29	13.735%	$111.7901	$111.79	$111.80	$111.80
Purchase #4	$48.91	11.644%	$54.6051	$54.61	$54.60	$54.60
Purchase #5	$110.93	4.774%	$116.2258	$116.23	$116.25	$116.20
Purchase #6	$157.63	10.683%	$174.4696	$174.47	$174.45	$174.50
Purchase #7	$223.73	10.841%	$247.9846	$247.98	$248.00	$248.00
7 purchase totals =	$793.47		$874.4479	$874.46	$874.45	$874.50