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	$78.71	5.102%	$82.7258	$82.73	$82.75	$82.70
Purchase #2	$201.73	6.618%	$215.0805	$215.08	$215.10	$215.10
Purchase #3	$95.44	3.799%	$99.0658	$99.07	$99.05	$99.10
Purchase #4	$91.46	8.200%	$98.9597	$98.96	$98.95	$99.00
Purchase #5	$136.78	7.313%	$146.7827	$146.78	$146.80	$146.80
Purchase #6	$54.86	10.133%	$60.419	$60.42	$60.40	$60.40
Purchase #7	$144.30	5.840%	$152.7271	$152.73	$152.75	$152.70
7 purchase totals =	$803.28		$855.7606	$855.77	$855.80	$855.80