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	$208.96	11.697%	$233.4021	$233.40	$233.40	$233.40
Purchase #2	$248.63	10.198%	$273.9853	$273.99	$274.00	$274.00
Purchase #3	$69.56	11.625%	$77.6464	$77.65	$77.65	$77.60
Purchase #4	$221.54	7.507%	$238.171	$238.17	$238.15	$238.20
Purchase #5	$42.54	11.204%	$47.3062	$47.31	$47.30	$47.30
Purchase #6	$155.79	6.292%	$165.5923	$165.59	$165.60	$165.60
Purchase #7	$116.43	13.191%	$131.7883	$131.79	$131.80	$131.80
7 purchase totals =	$1,063.45		$1,167.8916	$1,167.90	$1,167.90	$1,167.90