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	$96.46	9.584%	$105.7047	$105.70	$105.70	$105.70
Purchase #2	$63.55	11.747%	$71.0152	$71.02	$71.00	$71.00
Purchase #3	$76.39	8.146%	$82.6127	$82.61	$82.60	$82.60
Purchase #4	$11.49	3.439%	$11.8851	$11.89	$11.90	$11.90
Purchase #5	$177.59	8.296%	$192.3229	$192.32	$192.30	$192.30
Purchase #6	$243.71	5.256%	$256.5194	$256.52	$256.50	$256.50
Purchase #7	$187.46	10.743%	$207.5988	$207.60	$207.60	$207.60
7 purchase totals =	$856.65		$927.6588	$927.66	$927.60	$927.60