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	$171.56	6.643%	$182.9567	$182.96	$182.95	$183.00
Purchase #2	$129.72	10.110%	$142.8347	$142.83	$142.85	$142.80
Purchase #3	$119.54	5.838%	$126.5187	$126.52	$126.50	$126.50
Purchase #4	$33.33	9.706%	$36.565	$36.57	$36.55	$36.60
Purchase #5	$64.77	3.596%	$67.0991	$67.10	$67.10	$67.10
Purchase #6	$46.56	8.472%	$50.5046	$50.50	$50.50	$50.50
Purchase #7	$210.32	8.615%	$228.4391	$228.44	$228.45	$228.40
7 purchase totals =	$775.80		$834.9179	$834.92	$834.90	$834.90