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	$96.43	11.524%	$107.5426	$107.54	$107.55	$107.50
Purchase #2	$220.53	9.109%	$240.6181	$240.62	$240.60	$240.60
Purchase #3	$154.36	6.702%	$164.7052	$164.71	$164.70	$164.70
Purchase #4	$127.30	9.600%	$139.5208	$139.52	$139.50	$139.50
Purchase #5	$103.55	5.356%	$109.0961	$109.10	$109.10	$109.10
Purchase #6	$187.90	4.611%	$196.5641	$196.56	$196.55	$196.60
Purchase #7	$5.59	6.703%	$5.9647	$5.96	$5.95	$6.00
7 purchase totals =	$895.66		$964.0116	$964.01	$963.95	$964.00