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	$196.86	13.454%	$223.3455	$223.35	$223.35	$223.30
Purchase #2	$147.40	10.367%	$162.681	$162.68	$162.70	$162.70
Purchase #3	$19.83	13.429%	$22.493	$22.49	$22.50	$22.50
Purchase #4	$144.59	5.783%	$152.9516	$152.95	$152.95	$153.00
Purchase #5	$169.29	12.678%	$190.7526	$190.75	$190.75	$190.80
Purchase #6	$7.75	9.431%	$8.4809	$8.48	$8.50	$8.50
Purchase #7	$96.29	9.188%	$105.1371	$105.14	$105.15	$105.10
7 purchase totals =	$782.01		$865.8417	$865.84	$865.90	$865.90