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	$148.68	5.860%	$157.3926	$157.39	$157.40	$157.40
Purchase #2	$60.38	12.497%	$67.9257	$67.93	$67.95	$67.90
Purchase #3	$189.47	12.272%	$212.7218	$212.72	$212.70	$212.70
Purchase #4	$172.57	9.470%	$188.9124	$188.91	$188.90	$188.90
Purchase #5	$85.34	13.574%	$96.9241	$96.92	$96.90	$96.90
Purchase #6	$93.77	6.670%	$100.0245	$100.02	$100.00	$100.00
Purchase #7	$56.54	8.842%	$61.5393	$61.54	$61.55	$61.50
7 purchase totals =	$806.75		$885.4404	$885.43	$885.40	$885.30