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	$187.59	10.248%	$206.8142	$206.81	$206.80	$206.80
Purchase #2	$93.61	13.119%	$105.8907	$105.89	$105.90	$105.90
Purchase #3	$205.45	8.771%	$223.47	$223.47	$223.45	$223.50
Purchase #4	$161.78	6.304%	$171.9786	$171.98	$172.00	$172.00
Purchase #5	$76.26	7.613%	$82.0657	$82.07	$82.05	$82.10
Purchase #6	$197.31	9.599%	$216.2498	$216.25	$216.25	$216.20
Purchase #7	$139.96	5.112%	$147.1148	$147.11	$147.10	$147.10
7 purchase totals =	$1,061.96		$1,153.5838	$1,153.58	$1,153.55	$1,153.60