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	$215.78	4.669%	$225.8548	$225.85	$225.85	$225.90
Purchase #2	$200.33	13.248%	$226.8697	$226.87	$226.85	$226.90
Purchase #3	$226.51	13.298%	$256.6313	$256.63	$256.65	$256.60
Purchase #4	$14.58	11.837%	$16.3058	$16.31	$16.30	$16.30
Purchase #5	$96.36	7.455%	$103.5436	$103.54	$103.55	$103.50
Purchase #6	$124.71	13.741%	$141.8464	$141.85	$141.85	$141.80
Purchase #7	$26.56	4.873%	$27.8543	$27.85	$27.85	$27.90
7 purchase totals =	$904.83		$998.9059	$998.90	$998.90	$998.90