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	$12.66	12.298%	$14.2169	$14.22	$14.20	$14.20
Purchase #2	$61.25	9.836%	$67.2746	$67.27	$67.25	$67.30
Purchase #3	$235.52	12.479%	$264.9105	$264.91	$264.90	$264.90
Purchase #4	$72.51	8.818%	$78.9039	$78.90	$78.90	$78.90
Purchase #5	$28.82	8.115%	$31.1587	$31.16	$31.15	$31.20
Purchase #6	$227.27	11.632%	$253.706	$253.71	$253.70	$253.70
Purchase #7	$212.28	11.852%	$237.4394	$237.44	$237.45	$237.40
7 purchase totals =	$850.31		$947.6100	$947.61	$947.55	$947.60