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	$92.43	7.389%	$99.2597	$99.26	$99.25	$99.30
Purchase #2	$133.92	4.141%	$139.4656	$139.47	$139.45	$139.50
Purchase #3	$65.38	11.126%	$72.6542	$72.65	$72.65	$72.70
Purchase #4	$96.51	5.384%	$101.7061	$101.71	$101.70	$101.70
Purchase #5	$36.35	8.228%	$39.3409	$39.34	$39.35	$39.30
Purchase #6	$71.25	3.183%	$73.5179	$73.52	$73.50	$73.50
Purchase #7	$158.29	7.702%	$170.4815	$170.48	$170.50	$170.50
7 purchase totals =	$654.13		$696.4259	$696.43	$696.40	$696.50