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	$233.55	11.274%	$259.8804	$259.88	$259.90	$259.90
Purchase #2	$208.79	13.287%	$236.5319	$236.53	$236.55	$236.50
Purchase #3	$147.57	5.722%	$156.014	$156.01	$156.00	$156.00
Purchase #4	$198.68	4.801%	$208.2186	$208.22	$208.20	$208.20
Purchase #5	$150.84	11.691%	$168.4747	$168.47	$168.45	$168.50
Purchase #6	$191.92	4.419%	$200.4009	$200.40	$200.40	$200.40
Purchase #7	$203.56	9.499%	$222.8962	$222.90	$222.90	$222.90
7 purchase totals =	$1,334.91		$1,452.4167	$1,452.41	$1,452.40	$1,452.40