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	$35.53	7.505%	$38.1965	$38.20	$38.20	$38.20
Purchase #2	$112.96	4.102%	$117.5936	$117.59	$117.60	$117.60
Purchase #3	$10.25	11.153%	$11.3932	$11.39	$11.40	$11.40
Purchase #4	$42.58	7.807%	$45.9042	$45.90	$45.90	$45.90
Purchase #5	$16.39	13.371%	$18.5815	$18.58	$18.60	$18.60
Purchase #6	$79.81	11.530%	$89.0121	$89.01	$89.00	$89.00
Purchase #7	$30.35	10.459%	$33.5243	$33.52	$33.50	$33.50
7 purchase totals =	$327.87		$354.2054	$354.19	$354.20	$354.20