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	$80.31	3.472%	$83.0984	$83.10	$83.10	$83.10
Purchase #2	$107.30	10.112%	$118.1502	$118.15	$118.15	$118.20
Purchase #3	$143.45	6.324%	$152.5218	$152.52	$152.50	$152.50
Purchase #4	$186.80	7.312%	$200.4588	$200.46	$200.45	$200.50
Purchase #5	$121.68	4.665%	$127.3564	$127.36	$127.35	$127.40
Purchase #6	$58.91	8.528%	$63.9338	$63.93	$63.95	$63.90
Purchase #7	$231.73	3.103%	$238.9206	$238.92	$238.90	$238.90
7 purchase totals =	$930.18		$984.4400	$984.44	$984.40	$984.50