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	$161.85	12.664%	$182.3467	$182.35	$182.35	$182.30
Purchase #2	$118.63	7.119%	$127.0753	$127.08	$127.10	$127.10
Purchase #3	$215.86	5.400%	$227.5164	$227.52	$227.50	$227.50
Purchase #4	$28.79	12.601%	$32.4178	$32.42	$32.40	$32.40
Purchase #5	$176.89	8.474%	$191.8797	$191.88	$191.90	$191.90
Purchase #6	$126.56	6.327%	$134.5675	$134.57	$134.55	$134.60
Purchase #7	$223.30	3.462%	$231.0306	$231.03	$231.05	$231.00
7 purchase totals =	$1,051.88		$1,126.8340	$1,126.85	$1,126.85	$1,126.80