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	$109.63	4.289%	$114.332	$114.33	$114.35	$114.30
Purchase #2	$228.92	9.309%	$250.2302	$250.23	$250.25	$250.20
Purchase #3	$74.98	13.660%	$85.2223	$85.22	$85.20	$85.20
Purchase #4	$196.39	5.157%	$206.5178	$206.52	$206.50	$206.50
Purchase #5	$249.59	11.518%	$278.3378	$278.34	$278.35	$278.30
Purchase #6	$12.90	8.531%	$14.0005	$14.00	$14.00	$14.00
Purchase #7	$99.30	12.139%	$111.354	$111.35	$111.35	$111.40
7 purchase totals =	$971.71		$1,059.9946	$1,059.99	$1,060.00	$1,059.90