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	$60.50	9.468%	$66.2281	$66.23	$66.25	$66.20
Purchase #2	$225.45	13.606%	$256.1247	$256.12	$256.10	$256.10
Purchase #3	$233.82	3.737%	$242.5579	$242.56	$242.55	$242.60
Purchase #4	$58.51	10.843%	$64.8542	$64.85	$64.85	$64.90
Purchase #5	$58.81	12.501%	$66.1618	$66.16	$66.15	$66.20
Purchase #6	$135.94	9.199%	$148.4451	$148.45	$148.45	$148.40
Purchase #7	$200.40	4.416%	$209.2497	$209.25	$209.25	$209.20
7 purchase totals =	$973.43		$1,053.6215	$1,053.62	$1,053.60	$1,053.60