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	$199.31	5.223%	$209.72	$209.72	$209.70	$209.70
Purchase #2	$240.97	13.510%	$273.525	$273.53	$273.55	$273.50
Purchase #3	$54.29	8.547%	$58.9302	$58.93	$58.95	$58.90
Purchase #4	$22.90	8.440%	$24.8328	$24.83	$24.85	$24.80
Purchase #5	$162.49	5.689%	$171.7341	$171.73	$171.75	$171.70
Purchase #6	$57.78	7.130%	$61.8997	$61.90	$61.90	$61.90
Purchase #7	$241.66	8.670%	$262.6119	$262.61	$262.60	$262.60
7 purchase totals =	$979.40		$1,063.2537	$1,063.25	$1,063.30	$1,063.10