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	$77.67	6.796%	$82.9485	$82.95	$82.95	$82.90
Purchase #2	$28.70	9.867%	$31.5318	$31.53	$31.55	$31.50
Purchase #3	$92.41	8.126%	$99.9192	$99.92	$99.90	$99.90
Purchase #4	$216.88	11.823%	$242.5217	$242.52	$242.50	$242.50
Purchase #5	$162.77	8.601%	$176.7698	$176.77	$176.75	$176.80
Purchase #6	$167.84	11.440%	$187.0409	$187.04	$187.05	$187.00
Purchase #7	$133.90	5.179%	$140.8347	$140.83	$140.85	$140.80
7 purchase totals =	$880.17		$961.5666	$961.56	$961.55	$961.40