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	$79.54	9.270%	$86.9134	$86.91	$86.90	$86.90
Purchase #2	$113.84	10.263%	$125.5234	$125.52	$125.50	$125.50
Purchase #3	$197.38	12.475%	$222.0032	$222.00	$222.00	$222.00
Purchase #4	$62.86	5.351%	$66.2236	$66.22	$66.20	$66.20
Purchase #5	$94.88	6.337%	$100.8925	$100.89	$100.90	$100.90
Purchase #6	$220.35	13.297%	$249.6499	$249.65	$249.65	$249.60
Purchase #7	$167.94	10.664%	$185.8491	$185.85	$185.85	$185.80
7 purchase totals =	$936.79		$1,037.0551	$1,037.04	$1,037.00	$1,036.90