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	$89.45	6.811%	$95.5424	$95.54	$95.55	$95.50
Purchase #2	$125.27	6.547%	$133.4714	$133.47	$133.45	$133.50
Purchase #3	$207.55	4.544%	$216.9811	$216.98	$217.00	$217.00
Purchase #4	$64.41	10.610%	$71.2439	$71.24	$71.25	$71.20
Purchase #5	$41.72	4.227%	$43.4835	$43.48	$43.50	$43.50
Purchase #6	$44.59	8.109%	$48.2058	$48.21	$48.20	$48.20
Purchase #7	$35.93	9.407%	$39.3099	$39.31	$39.30	$39.30
7 purchase totals =	$608.92		$648.2380	$648.23	$648.25	$648.20