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	$41.56	4.189%	$43.3009	$43.30	$43.30	$43.30
Purchase #2	$23.90	3.312%	$24.6916	$24.69	$24.70	$24.70
Purchase #3	$143.34	3.797%	$148.7826	$148.78	$148.80	$148.80
Purchase #4	$122.48	3.106%	$126.2842	$126.28	$126.30	$126.30
Purchase #5	$124.50	5.366%	$131.1807	$131.18	$131.20	$131.20
Purchase #6	$137.56	10.156%	$151.5306	$151.53	$151.55	$151.50
Purchase #7	$225.83	10.206%	$248.8782	$248.88	$248.90	$248.90
7 purchase totals =	$819.17		$874.6488	$874.64	$874.75	$874.70