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	$93.63	12.868%	$105.6783	$105.68	$105.70	$105.70
Purchase #2	$87.95	12.705%	$99.124	$99.12	$99.10	$99.10
Purchase #3	$44.28	4.417%	$46.2358	$46.24	$46.25	$46.20
Purchase #4	$221.34	10.503%	$244.5873	$244.59	$244.60	$244.60
Purchase #5	$33.34	12.741%	$37.5878	$37.59	$37.60	$37.60
Purchase #6	$102.65	11.138%	$114.0832	$114.08	$114.10	$114.10
Purchase #7	$245.39	4.301%	$255.9442	$255.94	$255.95	$255.90
7 purchase totals =	$828.58		$903.2406	$903.24	$903.30	$903.20