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	$126.52	13.741%	$143.9051	$143.91	$143.90	$143.90
Purchase #2	$236.34	4.556%	$247.1077	$247.11	$247.10	$247.10
Purchase #3	$103.40	12.647%	$116.477	$116.48	$116.50	$116.50
Purchase #4	$181.35	8.428%	$196.6342	$196.63	$196.65	$196.60
Purchase #5	$106.46	8.468%	$115.475	$115.48	$115.50	$115.50
Purchase #6	$235.51	6.231%	$250.1846	$250.18	$250.20	$250.20
Purchase #7	$76.26	8.524%	$82.7604	$82.76	$82.75	$82.80
7 purchase totals =	$1,065.84		$1,152.5440	$1,152.55	$1,152.60	$1,152.60