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	$203.68	4.146%	$212.1246	$212.12	$212.10	$212.10
Purchase #2	$108.62	7.543%	$116.8132	$116.81	$116.80	$116.80
Purchase #3	$222.59	4.163%	$231.8564	$231.86	$231.85	$231.90
Purchase #4	$124.94	12.778%	$140.9048	$140.90	$140.90	$140.90
Purchase #5	$125.82	4.824%	$131.8896	$131.89	$131.90	$131.90
Purchase #6	$236.34	5.666%	$249.731	$249.73	$249.75	$249.70
Purchase #7	$192.67	12.874%	$217.4743	$217.47	$217.45	$217.50
7 purchase totals =	$1,214.66		$1,300.7939	$1,300.78	$1,300.75	$1,300.80