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	$66.54	7.126%	$71.2816	$71.28	$71.30	$71.30
Purchase #2	$193.31	3.164%	$199.4263	$199.43	$199.45	$199.40
Purchase #3	$38.69	6.840%	$41.3364	$41.34	$41.35	$41.30
Purchase #4	$161.87	8.446%	$175.5415	$175.54	$175.55	$175.50
Purchase #5	$235.49	6.228%	$250.1563	$250.16	$250.15	$250.20
Purchase #6	$199.52	7.239%	$213.9633	$213.96	$213.95	$214.00
Purchase #7	$137.39	10.447%	$151.7431	$151.74	$151.75	$151.70
7 purchase totals =	$1,032.81		$1,103.4485	$1,103.45	$1,103.50	$1,103.40