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	$160.76	7.309%	$172.5099	$172.51	$172.50	$172.50
Purchase #2	$15.27	8.624%	$16.5869	$16.59	$16.60	$16.60
Purchase #3	$36.44	10.305%	$40.1951	$40.20	$40.20	$40.20
Purchase #4	$220.60	10.841%	$244.5152	$244.52	$244.50	$244.50
Purchase #5	$51.30	3.396%	$53.0421	$53.04	$53.05	$53.00
Purchase #6	$202.46	7.744%	$218.1385	$218.14	$218.15	$218.10
Purchase #7	$184.89	12.804%	$208.5633	$208.56	$208.55	$208.60
7 purchase totals =	$871.72		$953.5510	$953.56	$953.55	$953.50