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	$30.45	8.358%	$32.995	$33.00	$33.00	$33.00
Purchase #2	$200.38	4.364%	$209.1246	$209.12	$209.10	$209.10
Purchase #3	$79.46	5.219%	$83.607	$83.61	$83.60	$83.60
Purchase #4	$186.43	7.214%	$199.8791	$199.88	$199.90	$199.90
Purchase #5	$155.44	5.643%	$164.2115	$164.21	$164.20	$164.20
Purchase #6	$250.76	11.448%	$279.467	$279.47	$279.45	$279.50
Purchase #7	$42.65	10.548%	$47.1487	$47.15	$47.15	$47.10
7 purchase totals =	$945.57		$1,016.4329	$1,016.44	$1,016.40	$1,016.40