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	$84.29	7.336%	$90.4735	$90.47	$90.45	$90.50
Purchase #2	$69.27	9.540%	$75.8784	$75.88	$75.90	$75.90
Purchase #3	$235.83	3.103%	$243.1478	$243.15	$243.15	$243.10
Purchase #4	$102.72	12.367%	$115.4234	$115.42	$115.40	$115.40
Purchase #5	$203.29	9.757%	$223.125	$223.13	$223.15	$223.10
Purchase #6	$50.83	5.270%	$53.5087	$53.51	$53.50	$53.50
Purchase #7	$88.48	6.409%	$94.1507	$94.15	$94.15	$94.20
7 purchase totals =	$834.71		$895.7075	$895.71	$895.70	$895.70