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	$211.97	13.566%	$240.7259	$240.73	$240.75	$240.70
Purchase #2	$95.98	10.319%	$105.8842	$105.88	$105.90	$105.90
Purchase #3	$83.96	3.761%	$87.1177	$87.12	$87.10	$87.10
Purchase #4	$48.58	13.227%	$55.0057	$55.01	$55.00	$55.00
Purchase #5	$143.92	13.809%	$163.7939	$163.79	$163.80	$163.80
Purchase #6	$234.79	9.240%	$256.4846	$256.48	$256.50	$256.50
Purchase #7	$99.95	10.596%	$110.5407	$110.54	$110.55	$110.50
7 purchase totals =	$919.15		$1,019.5527	$1,019.55	$1,019.60	$1,019.50