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	$42.68	6.803%	$45.5835	$45.58	$45.60	$45.60
Purchase #2	$74.94	9.542%	$82.0908	$82.09	$82.10	$82.10
Purchase #3	$215.92	3.692%	$223.8918	$223.89	$223.90	$223.90
Purchase #4	$100.68	13.807%	$114.5809	$114.58	$114.60	$114.60
Purchase #5	$182.85	11.352%	$203.6071	$203.61	$203.60	$203.60
Purchase #6	$67.95	3.472%	$70.3092	$70.31	$70.30	$70.30
Purchase #7	$85.67	8.643%	$93.0745	$93.07	$93.05	$93.10
7 purchase totals =	$770.69		$833.1378	$833.13	$833.15	$833.20