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	$219.38	7.375%	$235.5593	$235.56	$235.55	$235.60
Purchase #2	$19.39	5.281%	$20.414	$20.41	$20.40	$20.40
Purchase #3	$175.44	5.783%	$185.5857	$185.59	$185.60	$185.60
Purchase #4	$40.40	9.696%	$44.3172	$44.32	$44.30	$44.30
Purchase #5	$197.85	5.838%	$209.4005	$209.40	$209.40	$209.40
Purchase #6	$241.53	3.705%	$250.4787	$250.48	$250.50	$250.50
Purchase #7	$34.60	12.166%	$38.8094	$38.81	$38.80	$38.80
7 purchase totals =	$928.59		$984.5648	$984.57	$984.55	$984.60