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	$177.86	10.226%	$196.048	$196.05	$196.05	$196.00
Purchase #2	$133.90	6.319%	$142.3611	$142.36	$142.35	$142.40
Purchase #3	$211.55	3.212%	$218.345	$218.35	$218.35	$218.30
Purchase #4	$172.86	9.487%	$189.2592	$189.26	$189.25	$189.30
Purchase #5	$237.33	9.833%	$260.6667	$260.67	$260.65	$260.70
Purchase #6	$107.53	11.457%	$119.8497	$119.85	$119.85	$119.80
Purchase #7	$120.82	6.650%	$128.8545	$128.85	$128.85	$128.90
7 purchase totals =	$1,161.85		$1,255.3842	$1,255.39	$1,255.35	$1,255.40