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	$13.46	4.853%	$14.1132	$14.11	$14.10	$14.10
Purchase #2	$143.69	9.142%	$156.8261	$156.83	$156.85	$156.80
Purchase #3	$185.41	10.785%	$205.4065	$205.41	$205.40	$205.40
Purchase #4	$229.47	5.674%	$242.4901	$242.49	$242.50	$242.50
Purchase #5	$129.59	12.497%	$145.7849	$145.78	$145.80	$145.80
Purchase #6	$174.30	9.165%	$190.2746	$190.27	$190.25	$190.30
Purchase #7	$217.37	8.154%	$235.0943	$235.09	$235.10	$235.10
7 purchase totals =	$1,093.29		$1,189.9897	$1,189.98	$1,190.00	$1,190.00