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	$244.85	6.604%	$261.0199	$261.02	$261.00	$261.00
Purchase #2	$128.54	10.185%	$141.6318	$141.63	$141.65	$141.60
Purchase #3	$34.65	13.743%	$39.4119	$39.41	$39.40	$39.40
Purchase #4	$55.88	6.383%	$59.4468	$59.45	$59.45	$59.40
Purchase #5	$181.45	5.142%	$190.7802	$190.78	$190.80	$190.80
Purchase #6	$125.69	3.479%	$130.0628	$130.06	$130.05	$130.10
Purchase #7	$67.57	6.146%	$71.7229	$71.72	$71.70	$71.70
7 purchase totals =	$838.63		$894.0763	$894.07	$894.05	$894.00