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	$188.62	4.276%	$196.6854	$196.69	$196.70	$196.70
Purchase #2	$183.66	3.618%	$190.3048	$190.30	$190.30	$190.30
Purchase #3	$87.81	12.355%	$98.6589	$98.66	$98.65	$98.70
Purchase #4	$196.30	6.792%	$209.6327	$209.63	$209.65	$209.60
Purchase #5	$136.41	12.825%	$153.9046	$153.90	$153.90	$153.90
Purchase #6	$82.28	6.576%	$87.6907	$87.69	$87.70	$87.70
Purchase #7	$45.40	4.800%	$47.5792	$47.58	$47.60	$47.60
7 purchase totals =	$920.48		$984.4563	$984.45	$984.50	$984.50