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	$143.90	3.769%	$149.3236	$149.32	$149.30	$149.30
Purchase #2	$203.84	6.257%	$216.5943	$216.59	$216.60	$216.60
Purchase #3	$151.65	5.516%	$160.015	$160.02	$160.00	$160.00
Purchase #4	$86.26	4.770%	$90.3746	$90.37	$90.35	$90.40
Purchase #5	$157.46	5.352%	$165.8873	$165.89	$165.90	$165.90
Purchase #6	$207.92	7.338%	$223.1772	$223.18	$223.20	$223.20
Purchase #7	$50.25	12.242%	$56.4016	$56.40	$56.40	$56.40
7 purchase totals =	$1,001.28		$1,061.7736	$1,061.77	$1,061.75	$1,061.80