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	$81.52	12.571%	$91.7679	$91.77	$91.75	$91.80
Purchase #2	$161.25	13.385%	$182.8333	$182.83	$182.85	$182.80
Purchase #3	$42.74	7.138%	$45.7908	$45.79	$45.80	$45.80
Purchase #4	$151.34	11.403%	$168.5973	$168.60	$168.60	$168.60
Purchase #5	$237.92	10.197%	$262.1807	$262.18	$262.20	$262.20
Purchase #6	$38.43	4.810%	$40.2785	$40.28	$40.30	$40.30
Purchase #7	$220.55	5.675%	$233.0662	$233.07	$233.05	$233.10
7 purchase totals =	$933.75		$1,024.5147	$1,024.52	$1,024.55	$1,024.60