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	$134.43	5.602%	$141.9608	$141.96	$141.95	$142.00
Purchase #2	$83.85	10.851%	$92.9486	$92.95	$92.95	$92.90
Purchase #3	$131.38	11.620%	$146.6464	$146.65	$146.65	$146.60
Purchase #4	$69.31	3.649%	$71.8391	$71.84	$71.85	$71.80
Purchase #5	$127.67	6.749%	$136.2864	$136.29	$136.30	$136.30
Purchase #6	$206.66	4.526%	$216.0134	$216.01	$216.00	$216.00
Purchase #7	$57.43	3.604%	$59.4998	$59.50	$59.50	$59.50
7 purchase totals =	$810.73		$865.1945	$865.20	$865.20	$865.10