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	$198.85	10.325%	$219.3813	$219.38	$219.40	$219.40
Purchase #2	$155.89	8.593%	$169.2856	$169.29	$169.30	$169.30
Purchase #3	$33.26	10.538%	$36.7649	$36.76	$36.75	$36.80
Purchase #4	$164.91	6.592%	$175.7809	$175.78	$175.80	$175.80
Purchase #5	$52.57	13.241%	$59.5308	$59.53	$59.55	$59.50
Purchase #6	$117.56	8.470%	$127.5173	$127.52	$127.50	$127.50
Purchase #7	$180.73	4.294%	$188.4905	$188.49	$188.50	$188.50
7 purchase totals =	$903.77		$976.7513	$976.75	$976.80	$976.80