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	$128.86	3.202%	$132.9861	$132.99	$133.00	$133.00
Purchase #2	$195.53	11.682%	$218.3718	$218.37	$218.35	$218.40
Purchase #3	$120.53	11.777%	$134.7248	$134.72	$134.70	$134.70
Purchase #4	$18.25	12.335%	$20.5011	$20.50	$20.50	$20.50
Purchase #5	$39.43	6.576%	$42.0229	$42.02	$42.00	$42.00
Purchase #6	$14.47	4.679%	$15.1471	$15.15	$15.15	$15.10
Purchase #7	$33.69	11.283%	$37.4912	$37.49	$37.50	$37.50
7 purchase totals =	$550.76		$601.2450	$601.24	$601.20	$601.20