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	$172.44	5.581%	$182.0639	$182.06	$182.05	$182.10
Purchase #2	$16.27	13.776%	$18.5114	$18.51	$18.50	$18.50
Purchase #3	$92.76	10.104%	$102.1325	$102.13	$102.15	$102.10
Purchase #4	$104.86	4.743%	$109.8335	$109.83	$109.85	$109.80
Purchase #5	$108.58	9.622%	$119.0276	$119.03	$119.05	$119.00
Purchase #6	$129.51	9.117%	$141.3174	$141.32	$141.30	$141.30
Purchase #7	$131.46	5.814%	$139.1031	$139.10	$139.10	$139.10
7 purchase totals =	$755.88		$811.9894	$811.98	$812.00	$811.90