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	$59.45	7.513%	$63.9165	$63.92	$63.90	$63.90
Purchase #2	$77.56	5.679%	$81.9646	$81.96	$81.95	$82.00
Purchase #3	$157.93	12.781%	$178.115	$178.12	$178.10	$178.10
Purchase #4	$69.79	4.502%	$72.9319	$72.93	$72.95	$72.90
Purchase #5	$53.94	4.473%	$56.3527	$56.35	$56.35	$56.40
Purchase #6	$244.78	12.179%	$274.5918	$274.59	$274.60	$274.60
Purchase #7	$100.50	8.278%	$108.8194	$108.82	$108.80	$108.80
7 purchase totals =	$763.95		$836.6919	$836.69	$836.65	$836.70