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	$180.38	10.786%	$199.8358	$199.84	$199.85	$199.80
Purchase #2	$73.72	12.664%	$83.0559	$83.06	$83.05	$83.10
Purchase #3	$39.29	9.630%	$43.0736	$43.07	$43.05	$43.10
Purchase #4	$26.32	6.481%	$28.0258	$28.03	$28.05	$28.00
Purchase #5	$26.81	10.494%	$29.6234	$29.62	$29.60	$29.60
Purchase #6	$144.91	12.132%	$162.4905	$162.49	$162.50	$162.50
Purchase #7	$231.72	3.103%	$238.9103	$238.91	$238.90	$238.90
7 purchase totals =	$723.15		$785.0153	$785.02	$785.00	$785.00