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	$97.90	4.647%	$102.4494	$102.45	$102.45	$102.40
Purchase #2	$132.40	7.629%	$142.5008	$142.50	$142.50	$142.50
Purchase #3	$161.55	4.475%	$168.7794	$168.78	$168.80	$168.80
Purchase #4	$248.28	7.339%	$266.5013	$266.50	$266.50	$266.50
Purchase #5	$67.37	6.512%	$71.7571	$71.76	$71.75	$71.80
Purchase #6	$85.85	11.631%	$95.8352	$95.84	$95.85	$95.80
Purchase #7	$122.47	13.635%	$139.1688	$139.17	$139.15	$139.20
7 purchase totals =	$915.82		$986.9920	$987.00	$987.00	$987.00