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	$54.76	12.797%	$61.7676	$61.77	$61.75	$61.80
Purchase #2	$196.42	12.566%	$221.1021	$221.10	$221.10	$221.10
Purchase #3	$230.53	4.171%	$240.1454	$240.15	$240.15	$240.10
Purchase #4	$81.46	7.763%	$87.7837	$87.78	$87.80	$87.80
Purchase #5	$93.47	10.221%	$103.0236	$103.02	$103.00	$103.00
Purchase #6	$25.69	13.281%	$29.1019	$29.10	$29.10	$29.10
Purchase #7	$10.71	5.473%	$11.2962	$11.30	$11.30	$11.30
7 purchase totals =	$693.04		$754.2205	$754.22	$754.20	$754.20