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	$83.39	6.130%	$88.5018	$88.50	$88.50	$88.50
Purchase #2	$67.78	6.421%	$72.1322	$72.13	$72.15	$72.10
Purchase #3	$157.58	7.147%	$168.8422	$168.84	$168.85	$168.80
Purchase #4	$237.98	3.479%	$246.2593	$246.26	$246.25	$246.30
Purchase #5	$37.91	5.252%	$39.901	$39.90	$39.90	$39.90
Purchase #6	$180.99	13.861%	$206.077	$206.08	$206.10	$206.10
Purchase #7	$183.60	9.422%	$200.8988	$200.90	$200.90	$200.90
7 purchase totals =	$949.23		$1,022.6123	$1,022.61	$1,022.65	$1,022.60