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	$210.30	7.136%	$225.307	$225.31	$225.30	$225.30
Purchase #2	$236.64	6.150%	$251.1934	$251.19	$251.20	$251.20
Purchase #3	$179.53	11.837%	$200.781	$200.78	$200.80	$200.80
Purchase #4	$146.52	13.413%	$166.1727	$166.17	$166.15	$166.20
Purchase #5	$89.73	11.736%	$100.2607	$100.26	$100.25	$100.30
Purchase #6	$23.31	5.603%	$24.6161	$24.62	$24.60	$24.60
Purchase #7	$160.43	3.556%	$166.1349	$166.13	$166.15	$166.10
7 purchase totals =	$1,046.46		$1,134.4658	$1,134.46	$1,134.45	$1,134.50