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	$37.55	13.194%	$42.5043	$42.50	$42.50	$42.50
Purchase #2	$224.77	3.738%	$233.1719	$233.17	$233.15	$233.20
Purchase #3	$182.97	4.676%	$191.5257	$191.53	$191.55	$191.50
Purchase #4	$183.63	6.604%	$195.7569	$195.76	$195.75	$195.80
Purchase #5	$171.46	11.786%	$191.6683	$191.67	$191.65	$191.70
Purchase #6	$56.42	9.743%	$61.917	$61.92	$61.90	$61.90
Purchase #7	$112.45	3.662%	$116.5679	$116.57	$116.55	$116.60
7 purchase totals =	$969.25		$1,033.1120	$1,033.12	$1,033.05	$1,033.20