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	$84.44	13.214%	$95.5979	$95.60	$95.60	$95.60
Purchase #2	$88.75	13.354%	$100.6017	$100.60	$100.60	$100.60
Purchase #3	$219.58	7.270%	$235.5435	$235.54	$235.55	$235.50
Purchase #4	$47.72	5.428%	$50.3102	$50.31	$50.30	$50.30
Purchase #5	$246.79	10.847%	$273.5593	$273.56	$273.55	$273.60
Purchase #6	$66.63	7.825%	$71.8438	$71.84	$71.85	$71.80
Purchase #7	$150.49	12.808%	$169.7648	$169.76	$169.75	$169.80
7 purchase totals =	$904.40		$997.2212	$997.21	$997.20	$997.20