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	$130.74	4.732%	$136.9266	$136.93	$136.95	$136.90
Purchase #2	$225.45	13.690%	$256.3141	$256.31	$256.30	$256.30
Purchase #3	$31.73	3.282%	$32.7714	$32.77	$32.75	$32.80
Purchase #4	$20.66	11.729%	$23.0832	$23.08	$23.10	$23.10
Purchase #5	$85.40	12.862%	$96.3841	$96.38	$96.40	$96.40
Purchase #6	$47.71	13.508%	$54.1547	$54.15	$54.15	$54.20
Purchase #7	$6.51	13.301%	$7.3759	$7.38	$7.40	$7.40
7 purchase totals =	$548.20		$607.0100	$607.00	$607.05	$607.10