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	$98.88	6.867%	$105.6701	$105.67	$105.65	$105.70
Purchase #2	$184.69	13.297%	$209.2482	$209.25	$209.25	$209.20
Purchase #3	$126.86	11.110%	$140.9541	$140.95	$140.95	$141.00
Purchase #4	$119.92	8.756%	$130.4202	$130.42	$130.40	$130.40
Purchase #5	$196.35	13.854%	$223.5523	$223.55	$223.55	$223.60
Purchase #6	$154.89	4.471%	$161.8151	$161.82	$161.80	$161.80
Purchase #7	$80.82	12.381%	$90.8263	$90.83	$90.85	$90.80
7 purchase totals =	$962.41		$1,062.4863	$1,062.49	$1,062.45	$1,062.50