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	$193.88	12.560%	$218.2313	$218.23	$218.25	$218.20
Purchase #2	$41.53	6.667%	$44.2988	$44.30	$44.30	$44.30
Purchase #3	$129.36	11.730%	$144.5339	$144.53	$144.55	$144.50
Purchase #4	$242.73	11.193%	$269.8988	$269.90	$269.90	$269.90
Purchase #5	$113.65	11.591%	$126.8232	$126.82	$126.80	$126.80
Purchase #6	$94.50	5.861%	$100.0386	$100.04	$100.05	$100.00
Purchase #7	$160.63	4.577%	$167.982	$167.98	$168.00	$168.00
7 purchase totals =	$976.28		$1,071.8066	$1,071.80	$1,071.85	$1,071.70