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	$53.98	3.375%	$55.8018	$55.80	$55.80	$55.80
Purchase #2	$188.54	12.382%	$211.885	$211.89	$211.90	$211.90
Purchase #3	$139.26	3.691%	$144.4001	$144.40	$144.40	$144.40
Purchase #4	$94.66	5.802%	$100.1522	$100.15	$100.15	$100.20
Purchase #5	$40.42	11.707%	$45.152	$45.15	$45.15	$45.20
Purchase #6	$63.68	10.107%	$70.1161	$70.12	$70.10	$70.10
Purchase #7	$81.32	13.781%	$92.5267	$92.53	$92.55	$92.50
7 purchase totals =	$661.86		$720.0339	$720.04	$720.05	$720.10