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	$201.29	10.127%	$221.6746	$221.67	$221.65	$221.70
Purchase #2	$174.78	5.840%	$184.9872	$184.99	$185.00	$185.00
Purchase #3	$117.50	13.503%	$133.366	$133.37	$133.35	$133.40
Purchase #4	$54.72	9.456%	$59.8943	$59.89	$59.90	$59.90
Purchase #5	$158.32	3.725%	$164.2174	$164.22	$164.20	$164.20
Purchase #6	$145.51	13.740%	$165.5031	$165.50	$165.50	$165.50
Purchase #7	$190.52	9.860%	$209.3053	$209.31	$209.30	$209.30
7 purchase totals =	$1,042.64		$1,138.9479	$1,138.95	$1,138.90	$1,139.00