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	$226.47	5.486%	$238.8941	$238.89	$238.90	$238.90
Purchase #2	$164.87	4.316%	$171.9858	$171.99	$172.00	$172.00
Purchase #3	$198.33	6.687%	$211.5923	$211.59	$211.60	$211.60
Purchase #4	$88.99	12.535%	$100.1449	$100.14	$100.15	$100.10
Purchase #5	$216.51	3.387%	$223.8432	$223.84	$223.85	$223.80
Purchase #6	$68.26	9.706%	$74.8853	$74.89	$74.90	$74.90
Purchase #7	$226.70	10.659%	$250.864	$250.86	$250.85	$250.90
7 purchase totals =	$1,190.13		$1,272.2096	$1,272.20	$1,272.25	$1,272.20