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	$59.35	13.460%	$67.3385	$67.34	$67.35	$67.30
Purchase #2	$192.63	5.503%	$203.2304	$203.23	$203.25	$203.20
Purchase #3	$77.32	7.194%	$82.8824	$82.88	$82.90	$82.90
Purchase #4	$137.33	3.150%	$141.6559	$141.66	$141.65	$141.70
Purchase #5	$20.70	5.252%	$21.7872	$21.79	$21.80	$21.80
Purchase #6	$168.91	11.672%	$188.6252	$188.63	$188.65	$188.60
Purchase #7	$137.28	3.308%	$141.8212	$141.82	$141.80	$141.80
7 purchase totals =	$793.52		$847.3408	$847.35	$847.40	$847.30