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	$229.45	6.805%	$245.0641	$245.06	$245.05	$245.10
Purchase #2	$120.29	11.674%	$134.3327	$134.33	$134.35	$134.30
Purchase #3	$37.83	4.448%	$39.5127	$39.51	$39.50	$39.50
Purchase #4	$131.90	10.380%	$145.5912	$145.59	$145.60	$145.60
Purchase #5	$158.59	8.749%	$172.465	$172.47	$172.45	$172.50
Purchase #6	$7.25	8.685%	$7.8797	$7.88	$7.90	$7.90
Purchase #7	$71.81	13.629%	$81.597	$81.60	$81.60	$81.60
7 purchase totals =	$757.12		$826.4424	$826.44	$826.45	$826.50