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	$104.83	7.456%	$112.6461	$112.65	$112.65	$112.60
Purchase #2	$31.72	3.719%	$32.8997	$32.90	$32.90	$32.90
Purchase #3	$96.94	7.651%	$104.3569	$104.36	$104.35	$104.40
Purchase #4	$21.38	11.505%	$23.8398	$23.84	$23.85	$23.80
Purchase #5	$196.90	4.160%	$205.091	$205.09	$205.10	$205.10
Purchase #6	$200.83	11.263%	$223.4495	$223.45	$223.45	$223.40
Purchase #7	$6.73	6.711%	$7.1817	$7.18	$7.20	$7.20
7 purchase totals =	$659.33		$709.4647	$709.47	$709.50	$709.40