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	$228.72	12.315%	$256.8869	$256.89	$256.90	$256.90
Purchase #2	$59.65	11.475%	$66.4948	$66.49	$66.50	$66.50
Purchase #3	$135.67	5.812%	$143.5551	$143.56	$143.55	$143.60
Purchase #4	$133.71	3.167%	$137.9446	$137.94	$137.95	$137.90
Purchase #5	$184.54	6.732%	$196.9632	$196.96	$196.95	$197.00
Purchase #6	$144.48	5.324%	$152.1721	$152.17	$152.15	$152.20
Purchase #7	$231.50	5.608%	$244.4825	$244.48	$244.50	$244.50
7 purchase totals =	$1,118.27		$1,198.4992	$1,198.49	$1,198.50	$1,198.60