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	$180.35	8.863%	$196.3344	$196.33	$196.35	$196.30
Purchase #2	$244.27	3.603%	$253.071	$253.07	$253.05	$253.10
Purchase #3	$151.32	3.185%	$156.1395	$156.14	$156.15	$156.10
Purchase #4	$102.95	8.164%	$111.3548	$111.35	$111.35	$111.40
Purchase #5	$200.95	10.159%	$221.3645	$221.36	$221.35	$221.40
Purchase #6	$212.40	5.382%	$223.8314	$223.83	$223.85	$223.80
Purchase #7	$83.90	7.515%	$90.2051	$90.21	$90.20	$90.20
7 purchase totals =	$1,176.14		$1,252.3007	$1,252.29	$1,252.30	$1,252.30