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	$92.36	8.108%	$99.8485	$99.85	$99.85	$99.80
Purchase #2	$142.66	5.854%	$151.0113	$151.01	$151.00	$151.00
Purchase #3	$194.32	12.262%	$218.1475	$218.15	$218.15	$218.10
Purchase #4	$60.58	10.669%	$67.0433	$67.04	$67.05	$67.00
Purchase #5	$9.67	8.867%	$10.5274	$10.53	$10.55	$10.50
Purchase #6	$70.39	10.741%	$77.9506	$77.95	$77.95	$78.00
Purchase #7	$136.58	5.830%	$144.5426	$144.54	$144.55	$144.50
7 purchase totals =	$706.56		$769.0712	$769.07	$769.10	$768.90