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	$43.32	7.145%	$46.4152	$46.42	$46.40	$46.40
Purchase #2	$163.54	13.415%	$185.4789	$185.48	$185.50	$185.50
Purchase #3	$217.54	4.748%	$227.8688	$227.87	$227.85	$227.90
Purchase #4	$243.54	6.161%	$258.5445	$258.54	$258.55	$258.50
Purchase #5	$94.58	4.439%	$98.7784	$98.78	$98.80	$98.80
Purchase #6	$93.85	5.279%	$98.8043	$98.80	$98.80	$98.80
Purchase #7	$33.72	10.139%	$37.1389	$37.14	$37.15	$37.10
7 purchase totals =	$890.09		$953.0290	$953.03	$953.05	$953.00