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	$83.27	7.802%	$89.7667	$89.77	$89.75	$89.80
Purchase #2	$233.83	5.755%	$247.2869	$247.29	$247.30	$247.30
Purchase #3	$112.72	10.680%	$124.7585	$124.76	$124.75	$124.80
Purchase #4	$190.83	6.651%	$203.5221	$203.52	$203.50	$203.50
Purchase #5	$40.45	3.442%	$41.8423	$41.84	$41.85	$41.80
Purchase #6	$121.99	7.187%	$130.7574	$130.76	$130.75	$130.80
Purchase #7	$161.32	6.106%	$171.1702	$171.17	$171.15	$171.20
7 purchase totals =	$944.41		$1,009.1041	$1,009.11	$1,009.05	$1,009.20