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	$72.47	5.500%	$76.4559	$76.46	$76.45	$76.50
Purchase #2	$117.81	10.676%	$130.3874	$130.39	$130.40	$130.40
Purchase #3	$146.49	8.698%	$159.2317	$159.23	$159.25	$159.20
Purchase #4	$56.45	9.411%	$61.7625	$61.76	$61.75	$61.80
Purchase #5	$39.99	5.733%	$42.2826	$42.28	$42.30	$42.30
Purchase #6	$196.49	3.710%	$203.7798	$203.78	$203.80	$203.80
Purchase #7	$77.56	11.620%	$86.5725	$86.57	$86.55	$86.60
7 purchase totals =	$707.26		$760.4724	$760.47	$760.50	$760.60