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	$227.56	11.659%	$254.0912	$254.09	$254.10	$254.10
Purchase #2	$124.67	10.174%	$137.3539	$137.35	$137.35	$137.40
Purchase #3	$83.28	3.215%	$85.9575	$85.96	$85.95	$86.00
Purchase #4	$61.61	6.385%	$65.5438	$65.54	$65.55	$65.50
Purchase #5	$76.35	9.237%	$83.4024	$83.40	$83.40	$83.40
Purchase #6	$243.44	4.557%	$254.5336	$254.53	$254.55	$254.50
Purchase #7	$48.39	4.513%	$50.5738	$50.57	$50.55	$50.60
7 purchase totals =	$865.30		$931.4562	$931.44	$931.45	$931.50