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	$94.78	10.701%	$104.9224	$104.92	$104.90	$104.90
Purchase #2	$244.79	7.632%	$263.4724	$263.47	$263.45	$263.50
Purchase #3	$164.84	11.840%	$184.3571	$184.36	$184.35	$184.40
Purchase #4	$66.62	9.165%	$72.7257	$72.73	$72.75	$72.70
Purchase #5	$248.63	4.663%	$260.2236	$260.22	$260.20	$260.20
Purchase #6	$54.52	9.721%	$59.8199	$59.82	$59.80	$59.80
Purchase #7	$46.45	4.702%	$48.6341	$48.63	$48.65	$48.60
7 purchase totals =	$920.63		$994.1552	$994.15	$994.10	$994.10