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	$217.59	12.381%	$244.5298	$244.53	$244.55	$244.50
Purchase #2	$92.83	12.309%	$104.2564	$104.26	$104.25	$104.30
Purchase #3	$64.96	3.606%	$67.3025	$67.30	$67.30	$67.30
Purchase #4	$53.38	13.128%	$60.3877	$60.39	$60.40	$60.40
Purchase #5	$228.30	12.369%	$256.5384	$256.54	$256.55	$256.50
Purchase #6	$247.92	3.525%	$256.6592	$256.66	$256.65	$256.70
Purchase #7	$43.25	5.493%	$45.6257	$45.63	$45.65	$45.60
7 purchase totals =	$948.23		$1,035.2997	$1,035.31	$1,035.35	$1,035.30