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	$78.37	10.389%	$86.5119	$86.51	$86.50	$86.50
Purchase #2	$242.76	12.612%	$273.3769	$273.38	$273.40	$273.40
Purchase #3	$194.40	11.842%	$217.4208	$217.42	$217.40	$217.40
Purchase #4	$177.31	10.724%	$196.3247	$196.32	$196.30	$196.30
Purchase #5	$92.95	9.759%	$102.021	$102.02	$102.00	$102.00
Purchase #6	$32.56	9.709%	$35.7213	$35.72	$35.70	$35.70
Purchase #7	$108.29	13.586%	$123.0023	$123.00	$123.00	$123.00
7 purchase totals =	$926.64		$1,034.3789	$1,034.37	$1,034.30	$1,034.30