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	$93.27	3.769%	$96.7853	$96.79	$96.80	$96.80
Purchase #2	$210.70	5.497%	$222.2822	$222.28	$222.30	$222.30
Purchase #3	$88.28	13.526%	$100.2208	$100.22	$100.20	$100.20
Purchase #4	$73.77	12.866%	$83.2612	$83.26	$83.25	$83.30
Purchase #5	$131.72	3.679%	$136.566	$136.57	$136.55	$136.60
Purchase #6	$225.95	9.372%	$247.126	$247.13	$247.15	$247.10
Purchase #7	$58.37	12.134%	$65.4526	$65.45	$65.45	$65.50
7 purchase totals =	$882.06		$951.6941	$951.70	$951.70	$951.80