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	$121.80	10.489%	$134.5756	$134.58	$134.60	$134.60
Purchase #2	$53.42	3.588%	$55.3367	$55.34	$55.35	$55.30
Purchase #3	$97.69	7.590%	$105.1047	$105.10	$105.10	$105.10
Purchase #4	$242.80	11.871%	$271.6228	$271.62	$271.60	$271.60
Purchase #5	$56.61	8.680%	$61.5237	$61.52	$61.50	$61.50
Purchase #6	$245.76	6.671%	$262.1546	$262.15	$262.15	$262.20
Purchase #7	$137.60	11.378%	$153.2561	$153.26	$153.25	$153.30
7 purchase totals =	$955.68		$1,043.5742	$1,043.57	$1,043.55	$1,043.60