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	$119.38	7.553%	$128.3968	$128.40	$128.40	$128.40
Purchase #2	$157.74	5.579%	$166.5403	$166.54	$166.55	$166.50
Purchase #3	$126.36	6.677%	$134.7971	$134.80	$134.80	$134.80
Purchase #4	$118.49	4.488%	$123.8078	$123.81	$123.80	$123.80
Purchase #5	$245.88	6.252%	$261.2524	$261.25	$261.25	$261.30
Purchase #6	$141.56	3.304%	$146.2371	$146.24	$146.25	$146.20
Purchase #7	$85.46	11.524%	$95.3084	$95.31	$95.30	$95.30
7 purchase totals =	$994.87		$1,056.3399	$1,056.35	$1,056.35	$1,056.30