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	$82.30	7.305%	$88.312	$88.31	$88.30	$88.30
Purchase #2	$34.31	10.499%	$37.9122	$37.91	$37.90	$37.90
Purchase #3	$203.42	13.563%	$231.0099	$231.01	$231.00	$231.00
Purchase #4	$158.41	13.480%	$179.7637	$179.76	$179.75	$179.80
Purchase #5	$230.94	12.357%	$259.4773	$259.48	$259.50	$259.50
Purchase #6	$59.63	10.143%	$65.6783	$65.68	$65.70	$65.70
Purchase #7	$192.49	9.295%	$210.3819	$210.38	$210.40	$210.40
7 purchase totals =	$961.50		$1,072.5353	$1,072.53	$1,072.55	$1,072.60