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	$126.50	11.723%	$141.3296	$141.33	$141.35	$141.30
Purchase #2	$20.27	8.234%	$21.939	$21.94	$21.95	$21.90
Purchase #3	$38.41	13.831%	$43.7225	$43.72	$43.70	$43.70
Purchase #4	$32.95	4.439%	$34.4127	$34.41	$34.40	$34.40
Purchase #5	$111.82	3.196%	$115.3938	$115.39	$115.40	$115.40
Purchase #6	$171.33	11.741%	$191.4459	$191.45	$191.45	$191.40
Purchase #7	$19.34	3.755%	$20.0662	$20.07	$20.05	$20.10
7 purchase totals =	$520.62		$568.3097	$568.31	$568.30	$568.20