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	$185.93	3.587%	$192.5993	$192.60	$192.60	$192.60
Purchase #2	$43.80	5.852%	$46.3632	$46.36	$46.35	$46.40
Purchase #3	$98.30	6.228%	$104.4221	$104.42	$104.40	$104.40
Purchase #4	$64.40	3.265%	$66.5027	$66.50	$66.50	$66.50
Purchase #5	$219.46	7.714%	$236.3891	$236.39	$236.40	$236.40
Purchase #6	$50.64	3.134%	$52.2271	$52.23	$52.25	$52.20
Purchase #7	$37.26	13.648%	$42.3452	$42.35	$42.35	$42.30
7 purchase totals =	$699.79		$740.8487	$740.85	$740.85	$740.80