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	$99.92	13.187%	$113.0965	$113.10	$113.10	$113.10
Purchase #2	$144.72	10.503%	$159.9199	$159.92	$159.90	$159.90
Purchase #3	$145.39	10.475%	$160.6196	$160.62	$160.60	$160.60
Purchase #4	$204.59	8.809%	$222.6123	$222.61	$222.60	$222.60
Purchase #5	$51.86	7.367%	$55.6805	$55.68	$55.70	$55.70
Purchase #6	$110.36	9.733%	$121.1013	$121.10	$121.10	$121.10
Purchase #7	$248.99	7.424%	$267.475	$267.48	$267.50	$267.50
7 purchase totals =	$1,005.83		$1,100.5051	$1,100.51	$1,100.50	$1,100.50