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	$55.99	8.589%	$60.799	$60.80	$60.80	$60.80
Purchase #2	$200.46	10.498%	$221.5043	$221.50	$221.50	$221.50
Purchase #3	$95.73	9.529%	$104.8521	$104.85	$104.85	$104.90
Purchase #4	$137.62	7.268%	$147.6222	$147.62	$147.60	$147.60
Purchase #5	$198.46	5.577%	$209.5281	$209.53	$209.55	$209.50
Purchase #6	$39.98	7.212%	$42.8634	$42.86	$42.85	$42.90
Purchase #7	$146.99	5.768%	$155.4684	$155.47	$155.45	$155.50
7 purchase totals =	$875.23		$942.6375	$942.63	$942.60	$942.70