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	$117.95	10.730%	$130.606	$130.61	$130.60	$130.60
Purchase #2	$44.63	11.127%	$49.596	$49.60	$49.60	$49.60
Purchase #3	$106.72	8.197%	$115.4678	$115.47	$115.45	$115.50
Purchase #4	$81.68	4.813%	$85.6113	$85.61	$85.60	$85.60
Purchase #5	$72.91	13.464%	$82.7266	$82.73	$82.75	$82.70
Purchase #6	$156.56	3.221%	$161.6028	$161.60	$161.60	$161.60
Purchase #7	$29.77	11.872%	$33.3043	$33.30	$33.30	$33.30
7 purchase totals =	$610.22		$658.9148	$658.92	$658.90	$658.90