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	$248.67	7.628%	$267.6385	$267.64	$267.65	$267.60
Purchase #2	$159.33	12.689%	$179.5474	$179.55	$179.55	$179.50
Purchase #3	$246.64	7.129%	$264.223	$264.22	$264.20	$264.20
Purchase #4	$7.57	4.428%	$7.9052	$7.91	$7.90	$7.90
Purchase #5	$58.85	3.484%	$60.9003	$60.90	$60.90	$60.90
Purchase #6	$47.92	9.500%	$52.4724	$52.47	$52.45	$52.50
Purchase #7	$191.40	9.486%	$209.5562	$209.56	$209.55	$209.60
7 purchase totals =	$960.38		$1,042.2430	$1,042.25	$1,042.20	$1,042.20