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	$212.27	3.740%	$220.2089	$220.21	$220.20	$220.20
Purchase #2	$9.28	9.272%	$10.1404	$10.14	$10.15	$10.10
Purchase #3	$37.80	12.503%	$42.5261	$42.53	$42.55	$42.50
Purchase #4	$248.48	11.657%	$277.4453	$277.45	$277.45	$277.40
Purchase #5	$84.82	5.332%	$89.3426	$89.34	$89.35	$89.30
Purchase #6	$249.79	10.622%	$276.3227	$276.32	$276.30	$276.30
Purchase #7	$238.83	10.173%	$263.1262	$263.13	$263.15	$263.10
7 purchase totals =	$1,081.27		$1,179.1122	$1,179.12	$1,179.15	$1,178.90