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	$114.77	10.228%	$126.5087	$126.51	$126.50	$126.50
Purchase #2	$138.93	6.108%	$147.4158	$147.42	$147.40	$147.40
Purchase #3	$206.60	4.218%	$215.3144	$215.31	$215.30	$215.30
Purchase #4	$90.50	8.454%	$98.1509	$98.15	$98.15	$98.20
Purchase #5	$185.42	13.719%	$210.8578	$210.86	$210.85	$210.90
Purchase #6	$213.93	4.655%	$223.8884	$223.89	$223.90	$223.90
Purchase #7	$206.67	6.801%	$220.7256	$220.73	$220.75	$220.70
7 purchase totals =	$1,156.82		$1,242.8616	$1,242.87	$1,242.85	$1,242.90