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	$82.86	13.605%	$94.1331	$94.13	$94.15	$94.10
Purchase #2	$81.64	7.535%	$87.7916	$87.79	$87.80	$87.80
Purchase #3	$139.57	6.691%	$148.9086	$148.91	$148.90	$148.90
Purchase #4	$101.96	11.666%	$113.8547	$113.85	$113.85	$113.90
Purchase #5	$243.44	4.675%	$254.8208	$254.82	$254.80	$254.80
Purchase #6	$179.88	3.318%	$185.8484	$185.85	$185.85	$185.80
Purchase #7	$153.42	11.593%	$171.206	$171.21	$171.20	$171.20
7 purchase totals =	$982.77		$1,056.5632	$1,056.56	$1,056.55	$1,056.50