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	$174.87	9.244%	$191.035	$191.04	$191.05	$191.00
Purchase #2	$83.28	9.106%	$90.8635	$90.86	$90.85	$90.90
Purchase #3	$65.65	10.629%	$72.6279	$72.63	$72.65	$72.60
Purchase #4	$125.65	3.863%	$130.5039	$130.50	$130.50	$130.50
Purchase #5	$73.96	12.740%	$83.3825	$83.38	$83.40	$83.40
Purchase #6	$250.47	5.178%	$263.4393	$263.44	$263.45	$263.40
Purchase #7	$118.65	4.187%	$123.6179	$123.62	$123.60	$123.60
7 purchase totals =	$892.53		$955.4700	$955.47	$955.50	$955.40