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	$135.76	12.470%	$152.6893	$152.69	$152.70	$152.70
Purchase #2	$230.89	11.130%	$256.5881	$256.59	$256.60	$256.60
Purchase #3	$33.83	5.375%	$35.6484	$35.65	$35.65	$35.60
Purchase #4	$83.88	8.337%	$90.8731	$90.87	$90.85	$90.90
Purchase #5	$170.77	5.417%	$180.0206	$180.02	$180.00	$180.00
Purchase #6	$124.57	5.234%	$131.09	$131.09	$131.10	$131.10
Purchase #7	$114.69	9.657%	$125.7656	$125.77	$125.75	$125.80
7 purchase totals =	$894.39		$972.6751	$972.68	$972.65	$972.70