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	$206.60	7.641%	$222.3863	$222.39	$222.40	$222.40
Purchase #2	$101.78	11.542%	$113.5274	$113.53	$113.55	$113.50
Purchase #3	$127.53	13.299%	$144.4902	$144.49	$144.50	$144.50
Purchase #4	$153.74	9.819%	$168.8357	$168.84	$168.85	$168.80
Purchase #5	$215.59	10.417%	$238.048	$238.05	$238.05	$238.00
Purchase #6	$178.43	12.590%	$200.8943	$200.89	$200.90	$200.90
Purchase #7	$107.71	9.843%	$118.3119	$118.31	$118.30	$118.30
7 purchase totals =	$1,091.38		$1,206.4938	$1,206.50	$1,206.55	$1,206.40