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	$63.59	12.193%	$71.3435	$71.34	$71.35	$71.30
Purchase #2	$135.90	9.412%	$148.6909	$148.69	$148.70	$148.70
Purchase #3	$63.70	6.119%	$67.5978	$67.60	$67.60	$67.60
Purchase #4	$30.35	7.220%	$32.5413	$32.54	$32.55	$32.50
Purchase #5	$225.60	9.606%	$247.2711	$247.27	$247.25	$247.30
Purchase #6	$88.92	12.237%	$99.8011	$99.80	$99.80	$99.80
Purchase #7	$86.53	8.643%	$94.0088	$94.01	$94.00	$94.00
7 purchase totals =	$694.59		$761.2545	$761.25	$761.25	$761.20