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	$68.47	13.124%	$77.456	$77.46	$77.45	$77.50
Purchase #2	$18.89	3.415%	$19.5351	$19.54	$19.55	$19.50
Purchase #3	$250.46	13.344%	$283.8814	$283.88	$283.90	$283.90
Purchase #4	$122.89	13.481%	$139.4568	$139.46	$139.45	$139.50
Purchase #5	$75.74	13.200%	$85.7377	$85.74	$85.75	$85.70
Purchase #6	$35.56	7.131%	$38.0958	$38.10	$38.10	$38.10
Purchase #7	$41.31	10.321%	$45.5736	$45.57	$45.55	$45.60
7 purchase totals =	$613.32		$689.7364	$689.75	$689.75	$689.80