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	$38.43	4.738%	$40.2508	$40.25	$40.25	$40.30
Purchase #2	$188.71	10.572%	$208.6604	$208.66	$208.65	$208.70
Purchase #3	$54.43	12.470%	$61.2174	$61.22	$61.20	$61.20
Purchase #4	$151.61	10.463%	$167.473	$167.47	$167.45	$167.50
Purchase #5	$117.81	6.172%	$125.0812	$125.08	$125.10	$125.10
Purchase #6	$236.95	3.174%	$244.4708	$244.47	$244.45	$244.50
Purchase #7	$191.91	7.118%	$205.5702	$205.57	$205.55	$205.60
7 purchase totals =	$979.85		$1,052.7238	$1,052.72	$1,052.65	$1,052.90