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	$40.29	6.482%	$42.9016	$42.90	$42.90	$42.90
Purchase #2	$205.47	6.542%	$218.9118	$218.91	$218.90	$218.90
Purchase #3	$91.75	7.602%	$98.7248	$98.72	$98.70	$98.70
Purchase #4	$197.59	7.751%	$212.9052	$212.91	$212.90	$212.90
Purchase #5	$238.82	6.810%	$255.0836	$255.08	$255.10	$255.10
Purchase #6	$56.81	8.195%	$61.4656	$61.47	$61.45	$61.50
Purchase #7	$211.73	4.692%	$221.6644	$221.66	$221.65	$221.70
7 purchase totals =	$1,042.46		$1,111.6570	$1,111.65	$1,111.60	$1,111.70