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	$242.46	13.508%	$275.2115	$275.21	$275.20	$275.20
Purchase #2	$9.79	4.663%	$10.2465	$10.25	$10.25	$10.20
Purchase #3	$65.25	11.774%	$72.9325	$72.93	$72.95	$72.90
Purchase #4	$95.92	8.216%	$103.8008	$103.80	$103.80	$103.80
Purchase #5	$225.60	7.413%	$242.3237	$242.32	$242.30	$242.30
Purchase #6	$122.65	11.859%	$137.1951	$137.20	$137.20	$137.20
Purchase #7	$117.87	5.126%	$123.912	$123.91	$123.90	$123.90
7 purchase totals =	$879.54		$965.6221	$965.62	$965.60	$965.50