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	$222.45	5.117%	$233.8328	$233.83	$233.85	$233.80
Purchase #2	$64.48	4.602%	$67.4474	$67.45	$67.45	$67.40
Purchase #3	$209.97	12.424%	$236.0567	$236.06	$236.05	$236.10
Purchase #4	$95.61	3.778%	$99.2221	$99.22	$99.20	$99.20
Purchase #5	$57.59	7.389%	$61.8453	$61.85	$61.85	$61.80
Purchase #6	$130.43	8.174%	$141.0913	$141.09	$141.10	$141.10
Purchase #7	$36.59	3.593%	$37.9047	$37.90	$37.90	$37.90
7 purchase totals =	$817.12		$877.4003	$877.40	$877.40	$877.30