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	$187.89	11.651%	$209.7811	$209.78	$209.80	$209.80
Purchase #2	$57.47	3.359%	$59.4004	$59.40	$59.40	$59.40
Purchase #3	$23.61	11.446%	$26.3124	$26.31	$26.30	$26.30
Purchase #4	$235.89	3.365%	$243.8277	$243.83	$243.85	$243.80
Purchase #5	$87.94	11.807%	$98.3231	$98.32	$98.30	$98.30
Purchase #6	$5.49	7.286%	$5.89	$5.89	$5.90	$5.90
Purchase #7	$103.45	10.162%	$113.9626	$113.96	$113.95	$114.00
7 purchase totals =	$701.74		$757.4973	$757.49	$757.50	$757.50