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	$130.79	7.397%	$140.4645	$140.46	$140.45	$140.50
Purchase #2	$69.56	4.819%	$72.9121	$72.91	$72.90	$72.90
Purchase #3	$206.89	6.631%	$220.6089	$220.61	$220.60	$220.60
Purchase #4	$78.67	6.233%	$83.5735	$83.57	$83.55	$83.60
Purchase #5	$81.51	13.635%	$92.6239	$92.62	$92.60	$92.60
Purchase #6	$188.77	5.574%	$199.292	$199.29	$199.30	$199.30
Purchase #7	$5.54	10.750%	$6.1356	$6.14	$6.15	$6.10
7 purchase totals =	$761.73		$815.6105	$815.60	$815.55	$815.60