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	$217.94	12.708%	$245.6358	$245.64	$245.65	$245.60
Purchase #2	$86.64	7.206%	$92.8833	$92.88	$92.90	$92.90
Purchase #3	$223.54	3.756%	$231.9362	$231.94	$231.95	$231.90
Purchase #4	$77.78	13.155%	$88.012	$88.01	$88.00	$88.00
Purchase #5	$33.50	8.610%	$36.3844	$36.38	$36.40	$36.40
Purchase #6	$233.38	12.402%	$262.3238	$262.32	$262.30	$262.30
Purchase #7	$250.89	3.411%	$259.4479	$259.45	$259.45	$259.40
7 purchase totals =	$1,123.67		$1,216.6234	$1,216.62	$1,216.65	$1,216.50