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	$234.82	13.736%	$267.0749	$267.07	$267.05	$267.10
Purchase #2	$142.72	13.608%	$162.1413	$162.14	$162.15	$162.10
Purchase #3	$48.99	7.661%	$52.7431	$52.74	$52.75	$52.70
Purchase #4	$6.92	10.105%	$7.6193	$7.62	$7.60	$7.60
Purchase #5	$196.91	9.841%	$216.2879	$216.29	$216.30	$216.30
Purchase #6	$208.93	7.865%	$225.3623	$225.36	$225.35	$225.40
Purchase #7	$41.42	9.325%	$45.2824	$45.28	$45.30	$45.30
7 purchase totals =	$880.71		$976.5112	$976.50	$976.50	$976.50