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	$199.79	8.823%	$217.4175	$217.42	$217.40	$217.40
Purchase #2	$34.25	9.158%	$37.3866	$37.39	$37.40	$37.40
Purchase #3	$135.42	3.689%	$140.4156	$140.42	$140.40	$140.40
Purchase #4	$58.56	5.663%	$61.8763	$61.88	$61.90	$61.90
Purchase #5	$191.86	9.735%	$210.5376	$210.54	$210.55	$210.50
Purchase #6	$182.42	4.336%	$190.3297	$190.33	$190.35	$190.30
Purchase #7	$17.33	6.262%	$18.4152	$18.42	$18.40	$18.40
7 purchase totals =	$819.63		$876.3785	$876.40	$876.40	$876.30