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	$132.49	12.658%	$149.2606	$149.26	$149.25	$149.30
Purchase #2	$27.90	11.847%	$31.2053	$31.21	$31.20	$31.20
Purchase #3	$196.54	12.124%	$220.3685	$220.37	$220.35	$220.40
Purchase #4	$161.34	4.170%	$168.0679	$168.07	$168.05	$168.10
Purchase #5	$85.52	13.208%	$96.8155	$96.82	$96.80	$96.80
Purchase #6	$74.53	11.574%	$83.1561	$83.16	$83.15	$83.20
Purchase #7	$200.40	11.573%	$223.5923	$223.59	$223.60	$223.60
7 purchase totals =	$878.72		$972.4662	$972.48	$972.40	$972.60