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	$123.89	7.310%	$132.9464	$132.95	$132.95	$132.90
Purchase #2	$231.77	3.648%	$240.225	$240.23	$240.25	$240.20
Purchase #3	$240.66	9.853%	$264.3722	$264.37	$264.35	$264.40
Purchase #4	$234.93	4.758%	$246.108	$246.11	$246.10	$246.10
Purchase #5	$90.51	12.607%	$101.9206	$101.92	$101.90	$101.90
Purchase #6	$113.51	11.436%	$126.491	$126.49	$126.50	$126.50
Purchase #7	$98.39	13.618%	$111.7888	$111.79	$111.80	$111.80
7 purchase totals =	$1,133.66		$1,223.8520	$1,223.86	$1,223.85	$1,223.80