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	$164.81	12.733%	$185.7953	$185.80	$185.80	$185.80
Purchase #2	$96.69	12.283%	$108.5664	$108.57	$108.55	$108.60
Purchase #3	$184.59	3.506%	$191.0617	$191.06	$191.05	$191.10
Purchase #4	$131.63	11.210%	$146.3857	$146.39	$146.40	$146.40
Purchase #5	$191.45	13.138%	$216.6027	$216.60	$216.60	$216.60
Purchase #6	$177.56	7.805%	$191.4186	$191.42	$191.40	$191.40
Purchase #7	$20.94	8.360%	$22.6906	$22.69	$22.70	$22.70
7 purchase totals =	$967.67		$1,062.5210	$1,062.53	$1,062.50	$1,062.60