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	$22.79	11.807%	$25.4808	$25.48	$25.50	$25.50
Purchase #2	$59.28	6.709%	$63.2571	$63.26	$63.25	$63.30
Purchase #3	$109.40	13.170%	$123.808	$123.81	$123.80	$123.80
Purchase #4	$90.95	7.839%	$98.0796	$98.08	$98.10	$98.10
Purchase #5	$104.33	12.636%	$117.5131	$117.51	$117.50	$117.50
Purchase #6	$119.39	10.375%	$131.7767	$131.78	$131.80	$131.80
Purchase #7	$135.73	3.385%	$140.3245	$140.32	$140.30	$140.30
7 purchase totals =	$641.87		$700.2398	$700.24	$700.25	$700.30