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	$60.41	6.807%	$64.5221	$64.52	$64.50	$64.50
Purchase #2	$55.48	7.582%	$59.6865	$59.69	$59.70	$59.70
Purchase #3	$134.44	11.162%	$149.4462	$149.45	$149.45	$149.40
Purchase #4	$39.84	7.216%	$42.7149	$42.71	$42.70	$42.70
Purchase #5	$171.70	11.572%	$191.5691	$191.57	$191.55	$191.60
Purchase #6	$14.41	7.706%	$15.5204	$15.52	$15.50	$15.50
Purchase #7	$202.76	3.753%	$210.3696	$210.37	$210.35	$210.40
7 purchase totals =	$679.04		$733.8288	$733.83	$733.75	$733.80