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	$239.88	11.664%	$267.8596	$267.86	$267.85	$267.90
Purchase #2	$226.41	3.744%	$234.8868	$234.89	$234.90	$234.90
Purchase #3	$60.52	6.529%	$64.4714	$64.47	$64.45	$64.50
Purchase #4	$194.88	10.640%	$215.6152	$215.62	$215.60	$215.60
Purchase #5	$145.91	4.429%	$152.3724	$152.37	$152.35	$152.40
Purchase #6	$74.89	13.290%	$84.8429	$84.84	$84.85	$84.80
Purchase #7	$88.45	13.633%	$100.5084	$100.51	$100.50	$100.50
7 purchase totals =	$1,030.94		$1,120.5567	$1,120.56	$1,120.50	$1,120.60