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	$197.36	12.772%	$222.5668	$222.57	$222.55	$222.60
Purchase #2	$125.70	4.269%	$131.0661	$131.07	$131.05	$131.10
Purchase #3	$245.88	13.699%	$279.5631	$279.56	$279.55	$279.60
Purchase #4	$222.57	10.446%	$245.8197	$245.82	$245.80	$245.80
Purchase #5	$136.71	8.188%	$147.9038	$147.90	$147.90	$147.90
Purchase #6	$187.59	11.226%	$208.6489	$208.65	$208.65	$208.60
Purchase #7	$26.41	8.873%	$28.7534	$28.75	$28.75	$28.80
7 purchase totals =	$1,142.22		$1,264.3218	$1,264.32	$1,264.25	$1,264.40