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	$17.87	8.165%	$19.3291	$19.33	$19.35	$19.30
Purchase #2	$65.98	7.387%	$70.8539	$70.85	$70.85	$70.90
Purchase #3	$151.78	5.752%	$160.5104	$160.51	$160.50	$160.50
Purchase #4	$209.40	11.490%	$233.4601	$233.46	$233.45	$233.50
Purchase #5	$130.57	8.712%	$141.9453	$141.95	$141.95	$141.90
Purchase #6	$163.31	10.194%	$179.9578	$179.96	$179.95	$180.00
Purchase #7	$212.46	5.646%	$224.4555	$224.46	$224.45	$224.50
7 purchase totals =	$951.37		$1,030.5121	$1,030.52	$1,030.50	$1,030.60