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	$127.32	4.626%	$133.2098	$133.21	$133.20	$133.20
Purchase #2	$148.76	7.345%	$159.6864	$159.69	$159.70	$159.70
Purchase #3	$124.89	5.275%	$131.4779	$131.48	$131.50	$131.50
Purchase #4	$126.68	12.295%	$142.2553	$142.26	$142.25	$142.30
Purchase #5	$17.98	6.528%	$19.1537	$19.15	$19.15	$19.20
Purchase #6	$131.72	12.399%	$148.052	$148.05	$148.05	$148.10
Purchase #7	$131.56	7.483%	$141.4046	$141.40	$141.40	$141.40
7 purchase totals =	$808.91		$875.2397	$875.24	$875.25	$875.40