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	$220.80	13.853%	$251.3874	$251.39	$251.40	$251.40
Purchase #2	$6.87	3.767%	$7.1288	$7.13	$7.15	$7.10
Purchase #3	$99.41	13.245%	$112.5769	$112.58	$112.60	$112.60
Purchase #4	$245.57	6.577%	$261.7211	$261.72	$261.70	$261.70
Purchase #5	$30.75	3.722%	$31.8945	$31.89	$31.90	$31.90
Purchase #6	$129.81	9.694%	$142.3938	$142.39	$142.40	$142.40
Purchase #7	$184.32	13.823%	$209.7986	$209.80	$209.80	$209.80
7 purchase totals =	$917.53		$1,016.9011	$1,016.90	$1,016.95	$1,016.90