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	$94.74	7.795%	$102.125	$102.13	$102.15	$102.10
Purchase #2	$85.57	11.389%	$95.3156	$95.32	$95.30	$95.30
Purchase #3	$43.71	4.342%	$45.6079	$45.61	$45.60	$45.60
Purchase #4	$71.56	11.179%	$79.5597	$79.56	$79.55	$79.60
Purchase #5	$247.56	3.121%	$255.2863	$255.29	$255.30	$255.30
Purchase #6	$60.80	4.428%	$63.4922	$63.49	$63.50	$63.50
Purchase #7	$13.90	3.849%	$14.435	$14.44	$14.45	$14.40
7 purchase totals =	$617.84		$655.8217	$655.84	$655.85	$655.80