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	$188.56	10.327%	$208.0326	$208.03	$208.05	$208.00
Purchase #2	$30.50	5.600%	$32.208	$32.21	$32.20	$32.20
Purchase #3	$93.54	11.513%	$104.3093	$104.31	$104.30	$104.30
Purchase #4	$35.93	13.615%	$40.8219	$40.82	$40.80	$40.80
Purchase #5	$136.42	10.553%	$150.8164	$150.82	$150.80	$150.80
Purchase #6	$243.51	6.455%	$259.2286	$259.23	$259.25	$259.20
Purchase #7	$225.78	11.598%	$251.966	$251.97	$251.95	$252.00
7 purchase totals =	$954.24		$1,047.3828	$1,047.39	$1,047.35	$1,047.30