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	$61.44	8.764%	$66.8246	$66.82	$66.80	$66.80
Purchase #2	$7.52	4.401%	$7.851	$7.85	$7.85	$7.90
Purchase #3	$186.37	5.302%	$196.2513	$196.25	$196.25	$196.30
Purchase #4	$59.96	12.311%	$67.3417	$67.34	$67.35	$67.30
Purchase #5	$6.54	13.839%	$7.4451	$7.45	$7.45	$7.40
Purchase #6	$68.68	10.250%	$75.7197	$75.72	$75.70	$75.70
Purchase #7	$103.98	4.706%	$108.8733	$108.87	$108.85	$108.90
7 purchase totals =	$494.49		$530.3067	$530.30	$530.25	$530.30