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	$224.89	5.595%	$237.4726	$237.47	$237.45	$237.50
Purchase #2	$132.25	4.158%	$137.749	$137.75	$137.75	$137.70
Purchase #3	$240.73	10.731%	$266.5627	$266.56	$266.55	$266.60
Purchase #4	$217.44	10.803%	$240.93	$240.93	$240.95	$240.90
Purchase #5	$177.31	4.440%	$185.1826	$185.18	$185.20	$185.20
Purchase #6	$86.95	3.709%	$90.175	$90.18	$90.20	$90.20
Purchase #7	$12.46	13.179%	$14.1021	$14.10	$14.10	$14.10
7 purchase totals =	$1,092.03		$1,172.1740	$1,172.17	$1,172.20	$1,172.20