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	$132.96	10.460%	$146.8676	$146.87	$146.85	$146.90
Purchase #2	$36.97	6.487%	$39.3682	$39.37	$39.35	$39.40
Purchase #3	$197.39	13.287%	$223.6172	$223.62	$223.60	$223.60
Purchase #4	$245.97	13.666%	$279.5843	$279.58	$279.60	$279.60
Purchase #5	$106.32	5.219%	$111.8688	$111.87	$111.85	$111.90
Purchase #6	$242.55	9.526%	$265.6553	$265.66	$265.65	$265.70
Purchase #7	$86.73	6.463%	$92.3354	$92.34	$92.35	$92.30
7 purchase totals =	$1,048.89		$1,159.2968	$1,159.31	$1,159.25	$1,159.40