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	$182.32	5.675%	$192.6667	$192.67	$192.65	$192.70
Purchase #2	$134.28	12.105%	$150.5346	$150.53	$150.55	$150.50
Purchase #3	$243.65	6.649%	$259.8503	$259.85	$259.85	$259.90
Purchase #4	$25.38	3.531%	$26.2762	$26.28	$26.30	$26.30
Purchase #5	$80.79	10.783%	$89.5016	$89.50	$89.50	$89.50
Purchase #6	$229.31	11.180%	$254.9469	$254.95	$254.95	$254.90
Purchase #7	$216.90	11.162%	$241.1104	$241.11	$241.10	$241.10
7 purchase totals =	$1,112.63		$1,214.8867	$1,214.89	$1,214.90	$1,214.90