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	$225.51	7.465%	$242.3443	$242.34	$242.35	$242.30
Purchase #2	$209.31	13.788%	$238.1697	$238.17	$238.15	$238.20
Purchase #3	$167.52	3.182%	$172.8505	$172.85	$172.85	$172.90
Purchase #4	$66.89	8.448%	$72.5409	$72.54	$72.55	$72.50
Purchase #5	$223.69	5.165%	$235.2436	$235.24	$235.25	$235.20
Purchase #6	$109.80	11.343%	$122.2546	$122.25	$122.25	$122.30
Purchase #7	$93.58	13.754%	$106.451	$106.45	$106.45	$106.50
7 purchase totals =	$1,096.30		$1,189.8546	$1,189.84	$1,189.85	$1,189.90