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	$199.46	11.581%	$222.5595	$222.56	$222.55	$222.60
Purchase #2	$132.58	10.289%	$146.2212	$146.22	$146.20	$146.20
Purchase #3	$188.84	3.208%	$194.898	$194.90	$194.90	$194.90
Purchase #4	$141.53	3.737%	$146.819	$146.82	$146.80	$146.80
Purchase #5	$29.97	9.164%	$32.7165	$32.72	$32.70	$32.70
Purchase #6	$159.48	9.617%	$174.8172	$174.82	$174.80	$174.80
Purchase #7	$12.91	13.428%	$14.6436	$14.64	$14.65	$14.60
7 purchase totals =	$864.77		$932.6750	$932.68	$932.60	$932.60