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	$233.67	7.177%	$250.4405	$250.44	$250.45	$250.40
Purchase #2	$215.50	6.469%	$229.4407	$229.44	$229.45	$229.40
Purchase #3	$49.51	4.689%	$51.8315	$51.83	$51.85	$51.80
Purchase #4	$180.32	6.446%	$191.9434	$191.94	$191.95	$191.90
Purchase #5	$40.42	13.667%	$45.9442	$45.94	$45.95	$45.90
Purchase #6	$142.94	6.551%	$152.304	$152.30	$152.30	$152.30
Purchase #7	$113.90	5.239%	$119.8672	$119.87	$119.85	$119.90
7 purchase totals =	$976.26		$1,041.7715	$1,041.76	$1,041.80	$1,041.60