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	$110.95	4.726%	$116.1935	$116.19	$116.20	$116.20
Purchase #2	$71.57	10.149%	$78.8336	$78.83	$78.85	$78.80
Purchase #3	$125.74	10.193%	$138.5567	$138.56	$138.55	$138.60
Purchase #4	$91.93	13.731%	$104.5529	$104.55	$104.55	$104.60
Purchase #5	$137.60	12.231%	$154.4299	$154.43	$154.45	$154.40
Purchase #6	$214.84	3.183%	$221.6784	$221.68	$221.70	$221.70
Purchase #7	$92.87	7.556%	$99.8873	$99.89	$99.90	$99.90
7 purchase totals =	$845.50		$914.1323	$914.13	$914.20	$914.20