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	$43.36	5.765%	$45.8597	$45.86	$45.85	$45.90
Purchase #2	$238.32	10.860%	$264.2016	$264.20	$264.20	$264.20
Purchase #3	$13.26	6.609%	$14.1364	$14.14	$14.15	$14.10
Purchase #4	$31.53	4.310%	$32.8889	$32.89	$32.90	$32.90
Purchase #5	$142.66	7.552%	$153.4337	$153.43	$153.45	$153.40
Purchase #6	$139.81	8.265%	$151.3653	$151.37	$151.35	$151.40
Purchase #7	$213.50	13.682%	$242.7111	$242.71	$242.70	$242.70
7 purchase totals =	$822.44		$904.5967	$904.60	$904.60	$904.60