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	$211.43	5.356%	$222.7542	$222.75	$222.75	$222.80
Purchase #2	$33.91	3.325%	$35.0375	$35.04	$35.05	$35.00
Purchase #3	$28.76	10.175%	$31.6863	$31.69	$31.70	$31.70
Purchase #4	$91.89	13.712%	$104.49	$104.49	$104.50	$104.50
Purchase #5	$231.57	13.299%	$262.3665	$262.37	$262.35	$262.40
Purchase #6	$222.53	10.819%	$246.6055	$246.61	$246.60	$246.60
Purchase #7	$160.72	4.195%	$167.4622	$167.46	$167.45	$167.50
7 purchase totals =	$980.81		$1,070.4022	$1,070.41	$1,070.40	$1,070.50