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	$172.80	13.113%	$195.4593	$195.46	$195.45	$195.50
Purchase #2	$176.59	10.132%	$194.4821	$194.48	$194.50	$194.50
Purchase #3	$245.78	4.298%	$256.3436	$256.34	$256.35	$256.30
Purchase #4	$132.53	13.531%	$150.4626	$150.46	$150.45	$150.50
Purchase #5	$156.64	7.520%	$168.4193	$168.42	$168.40	$168.40
Purchase #6	$213.38	10.525%	$235.8382	$235.84	$235.85	$235.80
Purchase #7	$234.31	10.165%	$258.1276	$258.13	$258.15	$258.10
7 purchase totals =	$1,332.03		$1,459.1327	$1,459.13	$1,459.15	$1,459.10