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	$169.39	6.864%	$181.0169	$181.02	$181.00	$181.00
Purchase #2	$120.44	4.821%	$126.2464	$126.25	$126.25	$126.20
Purchase #3	$12.67	9.230%	$13.8394	$13.84	$13.85	$13.80
Purchase #4	$17.67	4.479%	$18.4614	$18.46	$18.45	$18.50
Purchase #5	$111.32	7.166%	$119.2972	$119.30	$119.30	$119.30
Purchase #6	$78.39	10.873%	$86.9133	$86.91	$86.90	$86.90
Purchase #7	$111.29	10.730%	$123.2314	$123.23	$123.25	$123.20
7 purchase totals =	$621.17		$669.0060	$669.01	$669.00	$668.90