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	$93.94	4.799%	$98.4482	$98.45	$98.45	$98.40
Purchase #2	$221.91	5.389%	$233.8687	$233.87	$233.85	$233.90
Purchase #3	$30.77	9.502%	$33.6938	$33.69	$33.70	$33.70
Purchase #4	$52.41	8.822%	$57.0336	$57.03	$57.05	$57.00
Purchase #5	$16.65	10.678%	$18.4279	$18.43	$18.45	$18.40
Purchase #6	$154.96	11.301%	$172.472	$172.47	$172.45	$172.50
Purchase #7	$175.81	3.620%	$182.1743	$182.17	$182.15	$182.20
7 purchase totals =	$746.45		$796.1185	$796.11	$796.10	$796.10