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	$245.96	10.515%	$271.8227	$271.82	$271.80	$271.80
Purchase #2	$236.82	4.702%	$247.9553	$247.96	$247.95	$248.00
Purchase #3	$155.66	7.843%	$167.8684	$167.87	$167.85	$167.90
Purchase #4	$97.44	5.139%	$102.4474	$102.45	$102.45	$102.40
Purchase #5	$6.97	10.580%	$7.7074	$7.71	$7.70	$7.70
Purchase #6	$154.27	7.447%	$165.7585	$165.76	$165.75	$165.80
Purchase #7	$132.32	3.794%	$137.3402	$137.34	$137.35	$137.30
7 purchase totals =	$1,029.44		$1,100.8999	$1,100.91	$1,100.85	$1,100.90