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	$57.98	4.549%	$60.6175	$60.62	$60.60	$60.60
Purchase #2	$20.35	10.709%	$22.5293	$22.53	$22.55	$22.50
Purchase #3	$245.43	8.835%	$267.1137	$267.11	$267.10	$267.10
Purchase #4	$124.25	3.396%	$128.4695	$128.47	$128.45	$128.50
Purchase #5	$96.68	4.399%	$100.933	$100.93	$100.95	$100.90
Purchase #6	$239.34	9.124%	$261.1774	$261.18	$261.20	$261.20
Purchase #7	$99.31	11.816%	$111.0445	$111.04	$111.05	$111.00
7 purchase totals =	$883.34		$951.8849	$951.88	$951.90	$951.80