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	$206.50	12.437%	$232.1824	$232.18	$232.20	$232.20
Purchase #2	$206.81	11.483%	$230.558	$230.56	$230.55	$230.60
Purchase #3	$214.34	5.392%	$225.8972	$225.90	$225.90	$225.90
Purchase #4	$133.58	12.206%	$149.8848	$149.88	$149.90	$149.90
Purchase #5	$53.90	10.214%	$59.4053	$59.41	$59.40	$59.40
Purchase #6	$90.97	4.791%	$95.3284	$95.33	$95.35	$95.30
Purchase #7	$37.80	13.320%	$42.835	$42.84	$42.85	$42.80
7 purchase totals =	$943.90		$1,036.0911	$1,036.10	$1,036.15	$1,036.10