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	$40.72	7.502%	$43.7748	$43.77	$43.75	$43.80
Purchase #2	$10.37	10.839%	$11.494	$11.49	$11.50	$11.50
Purchase #3	$66.92	8.110%	$72.3472	$72.35	$72.35	$72.30
Purchase #4	$32.83	12.488%	$36.9298	$36.93	$36.95	$36.90
Purchase #5	$243.67	10.241%	$268.6242	$268.62	$268.60	$268.60
Purchase #6	$47.53	11.514%	$53.0026	$53.00	$53.00	$53.00
Purchase #7	$17.99	5.278%	$18.9395	$18.94	$18.95	$18.90
7 purchase totals =	$460.03		$505.1121	$505.10	$505.10	$505.00