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	$186.67	11.511%	$208.1576	$208.16	$208.15	$208.20
Purchase #2	$85.31	11.531%	$95.1471	$95.15	$95.15	$95.10
Purchase #3	$146.85	9.240%	$160.4189	$160.42	$160.40	$160.40
Purchase #4	$78.92	6.241%	$83.8454	$83.85	$83.85	$83.80
Purchase #5	$65.75	3.326%	$67.9368	$67.94	$67.95	$67.90
Purchase #6	$125.92	8.355%	$136.4406	$136.44	$136.45	$136.40
Purchase #7	$233.39	13.528%	$264.963	$264.96	$264.95	$265.00
7 purchase totals =	$922.81		$1,016.9094	$1,016.92	$1,016.90	$1,016.80