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	$75.38	13.507%	$85.5616	$85.56	$85.55	$85.60
Purchase #2	$95.51	3.215%	$98.5806	$98.58	$98.60	$98.60
Purchase #3	$198.56	7.193%	$212.8424	$212.84	$212.85	$212.80
Purchase #4	$63.69	10.137%	$70.1463	$70.15	$70.15	$70.10
Purchase #5	$224.52	3.149%	$231.5901	$231.59	$231.60	$231.60
Purchase #6	$243.54	10.658%	$269.4965	$269.50	$269.50	$269.50
Purchase #7	$48.36	4.610%	$50.5894	$50.59	$50.60	$50.60
7 purchase totals =	$949.56		$1,018.8069	$1,018.81	$1,018.85	$1,018.80