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	$205.49	12.820%	$231.8338	$231.83	$231.85	$231.80
Purchase #2	$160.57	12.512%	$180.6605	$180.66	$180.65	$180.70
Purchase #3	$133.81	13.119%	$151.3645	$151.36	$151.35	$151.40
Purchase #4	$218.91	5.735%	$231.4645	$231.46	$231.45	$231.50
Purchase #5	$182.59	3.131%	$188.3069	$188.31	$188.30	$188.30
Purchase #6	$52.52	10.532%	$58.0514	$58.05	$58.05	$58.10
Purchase #7	$27.94	10.433%	$30.855	$30.86	$30.85	$30.90
7 purchase totals =	$981.83		$1,072.5366	$1,072.53	$1,072.50	$1,072.70