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	$203.81	6.265%	$216.5787	$216.58	$216.60	$216.60
Purchase #2	$106.29	5.680%	$112.3273	$112.33	$112.35	$112.30
Purchase #3	$107.39	11.681%	$119.9342	$119.93	$119.95	$119.90
Purchase #4	$27.73	5.700%	$29.3106	$29.31	$29.30	$29.30
Purchase #5	$243.35	13.234%	$275.5549	$275.55	$275.55	$275.60
Purchase #6	$231.39	10.776%	$256.3246	$256.32	$256.30	$256.30
Purchase #7	$184.80	11.380%	$205.8302	$205.83	$205.85	$205.80
7 purchase totals =	$1,104.76		$1,215.8605	$1,215.85	$1,215.90	$1,215.80