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	$185.79	12.739%	$209.4578	$209.46	$209.45	$209.50
Purchase #2	$76.73	12.557%	$86.365	$86.37	$86.35	$86.40
Purchase #3	$144.85	3.681%	$150.1819	$150.18	$150.20	$150.20
Purchase #4	$155.37	4.496%	$162.3554	$162.36	$162.35	$162.40
Purchase #5	$200.91	11.414%	$223.8419	$223.84	$223.85	$223.80
Purchase #6	$247.54	13.634%	$281.2896	$281.29	$281.30	$281.30
Purchase #7	$94.78	7.709%	$102.0866	$102.09	$102.10	$102.10
7 purchase totals =	$1,105.97		$1,215.5782	$1,215.59	$1,215.60	$1,215.70