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	$209.62	11.104%	$232.8962	$232.90	$232.90	$232.90
Purchase #2	$124.54	5.305%	$131.1468	$131.15	$131.15	$131.10
Purchase #3	$89.83	11.133%	$99.8308	$99.83	$99.85	$99.80
Purchase #4	$5.66	3.321%	$5.848	$5.85	$5.85	$5.80
Purchase #5	$85.98	11.595%	$95.9494	$95.95	$95.95	$95.90
Purchase #6	$35.99	11.541%	$40.1436	$40.14	$40.15	$40.10
Purchase #7	$18.50	9.104%	$20.1842	$20.18	$20.20	$20.20
7 purchase totals =	$570.12		$625.9990	$626.00	$626.05	$625.80