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	$217.70	3.400%	$225.1018	$225.10	$225.10	$225.10
Purchase #2	$158.61	6.460%	$168.8562	$168.86	$168.85	$168.90
Purchase #3	$239.80	8.237%	$259.5523	$259.55	$259.55	$259.60
Purchase #4	$163.57	4.586%	$171.0713	$171.07	$171.05	$171.10
Purchase #5	$94.38	13.817%	$107.4205	$107.42	$107.40	$107.40
Purchase #6	$186.84	3.246%	$192.9048	$192.90	$192.90	$192.90
Purchase #7	$63.83	12.800%	$72.0002	$72.00	$72.00	$72.00
7 purchase totals =	$1,124.73		$1,196.9071	$1,196.90	$1,196.85	$1,197.00