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	$25.86	9.567%	$28.334	$28.33	$28.35	$28.30
Purchase #2	$30.91	8.604%	$33.5695	$33.57	$33.55	$33.60
Purchase #3	$198.29	9.873%	$217.8672	$217.87	$217.85	$217.90
Purchase #4	$56.32	7.251%	$60.4038	$60.40	$60.40	$60.40
Purchase #5	$119.25	3.455%	$123.3701	$123.37	$123.35	$123.40
Purchase #6	$244.46	5.672%	$258.3258	$258.33	$258.35	$258.30
Purchase #7	$38.64	7.771%	$41.6427	$41.64	$41.65	$41.60
7 purchase totals =	$713.73		$763.5131	$763.51	$763.50	$763.50