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	$105.45	6.662%	$112.4751	$112.48	$112.50	$112.50
Purchase #2	$66.59	7.169%	$71.3638	$71.36	$71.35	$71.40
Purchase #3	$83.31	5.257%	$87.6896	$87.69	$87.70	$87.70
Purchase #4	$186.82	5.384%	$196.8784	$196.88	$196.90	$196.90
Purchase #5	$136.90	8.867%	$149.0389	$149.04	$149.05	$149.00
Purchase #6	$135.45	12.734%	$152.6982	$152.70	$152.70	$152.70
Purchase #7	$31.29	13.312%	$35.4553	$35.46	$35.45	$35.50
7 purchase totals =	$745.81		$805.5993	$805.61	$805.65	$805.70