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	$243.50	8.301%	$263.7129	$263.71	$263.70	$263.70
Purchase #2	$61.37	6.466%	$65.3382	$65.34	$65.35	$65.30
Purchase #3	$159.42	3.419%	$164.8706	$164.87	$164.85	$164.90
Purchase #4	$16.60	11.203%	$18.4597	$18.46	$18.45	$18.50
Purchase #5	$133.82	9.193%	$146.1221	$146.12	$146.10	$146.10
Purchase #6	$152.32	12.759%	$171.7545	$171.75	$171.75	$171.80
Purchase #7	$87.54	13.436%	$99.3019	$99.30	$99.30	$99.30
7 purchase totals =	$854.57		$929.5599	$929.55	$929.50	$929.60