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	$50.61	7.724%	$54.5191	$54.52	$54.50	$54.50
Purchase #2	$31.35	9.299%	$34.2652	$34.27	$34.25	$34.30
Purchase #3	$37.54	5.784%	$39.7113	$39.71	$39.70	$39.70
Purchase #4	$61.43	9.291%	$67.1375	$67.14	$67.15	$67.10
Purchase #5	$241.94	10.814%	$268.1034	$268.10	$268.10	$268.10
Purchase #6	$201.40	8.186%	$217.8866	$217.89	$217.90	$217.90
Purchase #7	$233.56	4.673%	$244.4743	$244.47	$244.45	$244.50
7 purchase totals =	$857.83		$926.0974	$926.10	$926.05	$926.10