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	$101.68	12.642%	$114.5344	$114.53	$114.55	$114.50
Purchase #2	$161.29	7.214%	$172.9255	$172.93	$172.95	$172.90
Purchase #3	$144.92	11.179%	$161.1206	$161.12	$161.10	$161.10
Purchase #4	$55.70	3.203%	$57.4841	$57.48	$57.50	$57.50
Purchase #5	$153.44	7.244%	$164.5552	$164.56	$164.55	$164.60
Purchase #6	$62.51	8.458%	$67.7971	$67.80	$67.80	$67.80
Purchase #7	$38.26	10.809%	$42.3955	$42.40	$42.40	$42.40
7 purchase totals =	$717.80		$780.8124	$780.82	$780.85	$780.80