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	$204.82	7.682%	$220.5543	$220.55	$220.55	$220.60
Purchase #2	$42.32	7.477%	$45.4843	$45.48	$45.50	$45.50
Purchase #3	$222.58	9.715%	$244.2036	$244.20	$244.20	$244.20
Purchase #4	$113.28	10.405%	$125.0668	$125.07	$125.05	$125.10
Purchase #5	$196.39	4.420%	$205.0704	$205.07	$205.05	$205.10
Purchase #6	$85.39	4.626%	$89.3401	$89.34	$89.35	$89.30
Purchase #7	$132.82	10.477%	$146.7356	$146.74	$146.75	$146.70
7 purchase totals =	$997.60		$1,076.4551	$1,076.45	$1,076.45	$1,076.50