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	$164.31	8.749%	$178.6855	$178.69	$178.70	$178.70
Purchase #2	$117.53	7.421%	$126.2519	$126.25	$126.25	$126.30
Purchase #3	$90.93	9.670%	$99.7229	$99.72	$99.70	$99.70
Purchase #4	$140.49	11.199%	$156.2235	$156.22	$156.20	$156.20
Purchase #5	$192.73	9.421%	$210.8871	$210.89	$210.90	$210.90
Purchase #6	$89.53	4.442%	$93.5069	$93.51	$93.50	$93.50
Purchase #7	$215.89	3.110%	$222.6042	$222.60	$222.60	$222.60
7 purchase totals =	$1,011.41		$1,087.8820	$1,087.88	$1,087.85	$1,087.90