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	$51.93	9.472%	$56.8488	$56.85	$56.85	$56.80
Purchase #2	$209.89	7.636%	$225.9172	$225.92	$225.90	$225.90
Purchase #3	$249.33	8.297%	$270.0169	$270.02	$270.00	$270.00
Purchase #4	$131.95	3.795%	$136.9575	$136.96	$136.95	$137.00
Purchase #5	$45.88	11.705%	$51.2503	$51.25	$51.25	$51.30
Purchase #6	$169.72	9.745%	$186.2592	$186.26	$186.25	$186.30
Purchase #7	$159.60	10.211%	$175.8968	$175.90	$175.90	$175.90
7 purchase totals =	$1,018.30		$1,103.1467	$1,103.16	$1,103.10	$1,103.20