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	$224.45	11.357%	$249.9408	$249.94	$249.95	$249.90
Purchase #2	$128.55	12.838%	$145.0532	$145.05	$145.05	$145.10
Purchase #3	$195.73	13.574%	$222.2984	$222.30	$222.30	$222.30
Purchase #4	$180.67	13.213%	$204.5419	$204.54	$204.55	$204.50
Purchase #5	$51.33	11.807%	$57.3905	$57.39	$57.40	$57.40
Purchase #6	$139.91	3.331%	$144.5704	$144.57	$144.55	$144.60
Purchase #7	$83.96	7.177%	$89.9858	$89.99	$90.00	$90.00
7 purchase totals =	$1,004.60		$1,113.7810	$1,113.78	$1,113.80	$1,113.80