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	$160.83	4.814%	$168.5724	$168.57	$168.55	$168.60
Purchase #2	$195.35	7.732%	$210.4545	$210.45	$210.45	$210.50
Purchase #3	$217.67	12.572%	$245.0355	$245.04	$245.05	$245.00
Purchase #4	$16.69	9.321%	$18.2457	$18.25	$18.25	$18.20
Purchase #5	$86.43	5.123%	$90.8578	$90.86	$90.85	$90.90
Purchase #6	$152.60	3.785%	$158.3759	$158.38	$158.40	$158.40
Purchase #7	$198.50	6.303%	$211.0115	$211.01	$211.00	$211.00
7 purchase totals =	$1,028.07		$1,102.5533	$1,102.56	$1,102.55	$1,102.60