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	$144.83	4.214%	$150.9331	$150.93	$150.95	$150.90
Purchase #2	$68.38	5.607%	$72.2141	$72.21	$72.20	$72.20
Purchase #3	$129.91	11.281%	$144.5651	$144.57	$144.55	$144.60
Purchase #4	$247.35	7.153%	$265.0429	$265.04	$265.05	$265.00
Purchase #5	$35.47	12.533%	$39.9155	$39.92	$39.90	$39.90
Purchase #6	$244.32	7.143%	$261.7718	$261.77	$261.75	$261.80
Purchase #7	$109.62	13.530%	$124.4516	$124.45	$124.45	$124.50
7 purchase totals =	$979.88		$1,058.8941	$1,058.89	$1,058.85	$1,058.90