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	$102.27	11.681%	$114.2162	$114.22	$114.20	$114.20
Purchase #2	$37.83	7.553%	$40.6873	$40.69	$40.70	$40.70
Purchase #3	$61.52	9.320%	$67.2537	$67.25	$67.25	$67.30
Purchase #4	$205.52	5.709%	$217.2531	$217.25	$217.25	$217.30
Purchase #5	$97.90	7.774%	$105.5107	$105.51	$105.50	$105.50
Purchase #6	$65.96	8.728%	$71.717	$71.72	$71.70	$71.70
Purchase #7	$150.34	5.239%	$158.2163	$158.22	$158.20	$158.20
7 purchase totals =	$721.34		$774.8543	$774.86	$774.80	$774.90