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	$68.25	13.609%	$77.5381	$77.54	$77.55	$77.50
Purchase #2	$41.80	9.140%	$45.6205	$45.62	$45.60	$45.60
Purchase #3	$213.50	11.545%	$238.1486	$238.15	$238.15	$238.10
Purchase #4	$148.39	5.643%	$156.7636	$156.76	$156.75	$156.80
Purchase #5	$107.53	9.227%	$117.4518	$117.45	$117.45	$117.50
Purchase #6	$232.86	3.319%	$240.5886	$240.59	$240.60	$240.60
Purchase #7	$100.69	8.722%	$109.4722	$109.47	$109.45	$109.50
7 purchase totals =	$913.02		$985.5834	$985.58	$985.55	$985.60