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	$154.50	13.363%	$175.1458	$175.15	$175.15	$175.10
Purchase #2	$20.54	4.547%	$21.474	$21.47	$21.45	$21.50
Purchase #3	$195.70	11.113%	$217.4481	$217.45	$217.45	$217.40
Purchase #4	$92.83	6.528%	$98.8899	$98.89	$98.90	$98.90
Purchase #5	$100.78	3.642%	$104.4504	$104.45	$104.45	$104.50
Purchase #6	$168.62	5.814%	$178.4236	$178.42	$178.40	$178.40
Purchase #7	$29.27	5.187%	$30.7882	$30.79	$30.80	$30.80
7 purchase totals =	$762.24		$826.6200	$826.62	$826.60	$826.60