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	$111.39	5.631%	$117.6624	$117.66	$117.65	$117.70
Purchase #2	$128.56	6.291%	$136.6477	$136.65	$136.65	$136.60
Purchase #3	$86.84	10.417%	$95.8861	$95.89	$95.90	$95.90
Purchase #4	$129.84	3.518%	$134.4078	$134.41	$134.40	$134.40
Purchase #5	$69.44	4.630%	$72.6551	$72.66	$72.65	$72.70
Purchase #6	$81.72	5.270%	$86.0266	$86.03	$86.05	$86.00
Purchase #7	$69.42	4.749%	$72.7168	$72.72	$72.70	$72.70
7 purchase totals =	$677.21		$716.0025	$716.02	$716.00	$716.00