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	$118.89	6.483%	$126.5976	$126.60	$126.60	$126.60
Purchase #2	$40.92	3.580%	$42.3849	$42.38	$42.40	$42.40
Purchase #3	$239.38	13.609%	$271.9572	$271.96	$271.95	$272.00
Purchase #4	$174.74	10.404%	$192.9199	$192.92	$192.90	$192.90
Purchase #5	$161.89	5.862%	$171.38	$171.38	$171.40	$171.40
Purchase #6	$84.99	11.430%	$94.7044	$94.70	$94.70	$94.70
Purchase #7	$92.53	10.833%	$102.5538	$102.55	$102.55	$102.60
7 purchase totals =	$913.34		$1,002.4978	$1,002.49	$1,002.50	$1,002.60