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	$204.39	10.290%	$225.4217	$225.42	$225.40	$225.40
Purchase #2	$99.58	10.105%	$109.6426	$109.64	$109.65	$109.60
Purchase #3	$170.45	13.601%	$193.6329	$193.63	$193.65	$193.60
Purchase #4	$175.37	8.155%	$189.6714	$189.67	$189.65	$189.70
Purchase #5	$76.67	13.331%	$86.8909	$86.89	$86.90	$86.90
Purchase #6	$109.61	3.850%	$113.83	$113.83	$113.85	$113.80
Purchase #7	$90.96	10.503%	$100.5135	$100.51	$100.50	$100.50
7 purchase totals =	$927.03		$1,019.6030	$1,019.59	$1,019.60	$1,019.50