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	$210.78	3.104%	$217.3226	$217.32	$217.30	$217.30
Purchase #2	$191.26	8.134%	$206.8171	$206.82	$206.80	$206.80
Purchase #3	$122.27	12.429%	$137.4669	$137.47	$137.45	$137.50
Purchase #4	$160.86	5.149%	$169.1427	$169.14	$169.15	$169.10
Purchase #5	$142.35	7.155%	$152.5351	$152.54	$152.55	$152.50
Purchase #6	$121.59	7.421%	$130.6132	$130.61	$130.60	$130.60
Purchase #7	$38.50	5.486%	$40.6121	$40.61	$40.60	$40.60
7 purchase totals =	$987.61		$1,054.5097	$1,054.51	$1,054.45	$1,054.40