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	$130.27	5.273%	$137.1391	$137.14	$137.15	$137.10
Purchase #2	$220.88	5.374%	$232.7501	$232.75	$232.75	$232.80
Purchase #3	$103.75	7.778%	$111.8197	$111.82	$111.80	$111.80
Purchase #4	$98.98	3.158%	$102.1058	$102.11	$102.10	$102.10
Purchase #5	$247.35	3.263%	$255.421	$255.42	$255.40	$255.40
Purchase #6	$207.82	7.619%	$223.6538	$223.65	$223.65	$223.70
Purchase #7	$56.87	8.217%	$61.543	$61.54	$61.55	$61.50
7 purchase totals =	$1,065.92		$1,124.4325	$1,124.43	$1,124.40	$1,124.40