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	$205.88	3.805%	$213.7137	$213.71	$213.70	$213.70
Purchase #2	$186.72	7.121%	$200.0163	$200.02	$200.00	$200.00
Purchase #3	$86.85	4.634%	$90.8746	$90.87	$90.85	$90.90
Purchase #4	$101.87	9.193%	$111.2349	$111.23	$111.25	$111.20
Purchase #5	$20.27	9.835%	$22.2636	$22.26	$22.25	$22.30
Purchase #6	$50.56	5.784%	$53.4844	$53.48	$53.50	$53.50
Purchase #7	$71.59	8.622%	$77.7625	$77.76	$77.75	$77.80
7 purchase totals =	$723.74		$769.3500	$769.33	$769.30	$769.40