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	$94.47	5.351%	$99.5251	$99.53	$99.55	$99.50
Purchase #2	$100.33	11.327%	$111.6944	$111.69	$111.70	$111.70
Purchase #3	$250.50	3.620%	$259.5681	$259.57	$259.55	$259.60
Purchase #4	$235.25	10.125%	$259.0691	$259.07	$259.05	$259.10
Purchase #5	$139.80	9.832%	$153.5451	$153.55	$153.55	$153.50
Purchase #6	$30.64	9.220%	$33.465	$33.47	$33.45	$33.50
Purchase #7	$108.97	8.164%	$117.8663	$117.87	$117.85	$117.90
7 purchase totals =	$959.96		$1,034.7331	$1,034.75	$1,034.70	$1,034.80