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	$234.30	3.690%	$242.9457	$242.95	$242.95	$242.90
Purchase #2	$5.61	10.592%	$6.2042	$6.20	$6.20	$6.20
Purchase #3	$13.48	10.379%	$14.8791	$14.88	$14.90	$14.90
Purchase #4	$86.87	3.124%	$89.5838	$89.58	$89.60	$89.60
Purchase #5	$25.34	12.447%	$28.4941	$28.49	$28.50	$28.50
Purchase #6	$202.82	7.766%	$218.571	$218.57	$218.55	$218.60
Purchase #7	$117.58	8.201%	$127.2227	$127.22	$127.20	$127.20
7 purchase totals =	$686.00		$727.9006	$727.89	$727.90	$727.90