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	$90.58	12.736%	$102.1163	$102.12	$102.10	$102.10
Purchase #2	$110.87	13.298%	$125.6135	$125.61	$125.60	$125.60
Purchase #3	$231.47	13.225%	$262.0819	$262.08	$262.10	$262.10
Purchase #4	$10.81	10.492%	$11.9442	$11.94	$11.95	$11.90
Purchase #5	$200.74	9.459%	$219.728	$219.73	$219.75	$219.70
Purchase #6	$126.33	10.725%	$139.8789	$139.88	$139.90	$139.90
Purchase #7	$105.93	5.602%	$111.8642	$111.86	$111.85	$111.90
7 purchase totals =	$876.73		$973.2270	$973.22	$973.25	$973.20