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	$215.93	7.341%	$231.7814	$231.78	$231.80	$231.80
Purchase #2	$217.38	8.678%	$236.2442	$236.24	$236.25	$236.20
Purchase #3	$196.92	6.292%	$209.3102	$209.31	$209.30	$209.30
Purchase #4	$42.99	6.645%	$45.8467	$45.85	$45.85	$45.80
Purchase #5	$174.46	3.485%	$180.5399	$180.54	$180.55	$180.50
Purchase #6	$153.53	12.370%	$172.5217	$172.52	$172.50	$172.50
Purchase #7	$77.76	7.503%	$83.5943	$83.59	$83.60	$83.60
7 purchase totals =	$1,078.97		$1,159.8384	$1,159.83	$1,159.85	$1,159.70