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	$103.91	10.585%	$114.9089	$114.91	$114.90	$114.90
Purchase #2	$110.78	6.299%	$117.758	$117.76	$117.75	$117.80
Purchase #3	$229.67	5.478%	$242.2513	$242.25	$242.25	$242.30
Purchase #4	$187.94	3.700%	$194.8938	$194.89	$194.90	$194.90
Purchase #5	$237.48	10.674%	$262.8286	$262.83	$262.85	$262.80
Purchase #6	$9.50	7.782%	$10.2393	$10.24	$10.25	$10.20
Purchase #7	$212.50	5.686%	$224.5828	$224.58	$224.60	$224.60
7 purchase totals =	$1,091.78		$1,167.4627	$1,167.46	$1,167.50	$1,167.50