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	$125.42	5.139%	$131.8653	$131.87	$131.85	$131.90
Purchase #2	$66.43	8.588%	$72.135	$72.14	$72.15	$72.10
Purchase #3	$138.40	13.843%	$157.5587	$157.56	$157.55	$157.60
Purchase #4	$88.58	5.607%	$93.5467	$93.55	$93.55	$93.50
Purchase #5	$17.75	3.869%	$18.4367	$18.44	$18.45	$18.40
Purchase #6	$161.62	11.258%	$179.8152	$179.82	$179.80	$179.80
Purchase #7	$151.86	13.327%	$172.0984	$172.10	$172.10	$172.10
7 purchase totals =	$750.06		$825.4560	$825.48	$825.45	$825.40