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	$64.30	4.309%	$67.0707	$67.07	$67.05	$67.10
Purchase #2	$195.59	9.107%	$213.4024	$213.40	$213.40	$213.40
Purchase #3	$34.38	9.676%	$37.7066	$37.71	$37.70	$37.70
Purchase #4	$48.30	13.748%	$54.9403	$54.94	$54.95	$54.90
Purchase #5	$249.86	4.183%	$260.3116	$260.31	$260.30	$260.30
Purchase #6	$57.66	3.443%	$59.6452	$59.65	$59.65	$59.60
Purchase #7	$118.30	8.345%	$128.1721	$128.17	$128.15	$128.20
7 purchase totals =	$768.39		$821.2489	$821.25	$821.20	$821.20