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	$151.30	9.661%	$165.9171	$165.92	$165.90	$165.90
Purchase #2	$188.34	6.680%	$200.9211	$200.92	$200.90	$200.90
Purchase #3	$59.84	7.361%	$64.2448	$64.24	$64.25	$64.20
Purchase #4	$41.47	9.301%	$45.3271	$45.33	$45.35	$45.30
Purchase #5	$169.86	3.445%	$175.7117	$175.71	$175.70	$175.70
Purchase #6	$59.93	9.487%	$65.6156	$65.62	$65.60	$65.60
Purchase #7	$234.98	11.589%	$262.2118	$262.21	$262.20	$262.20
7 purchase totals =	$905.72		$979.9492	$979.95	$979.90	$979.80