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	$245.63	4.585%	$256.8921	$256.89	$256.90	$256.90
Purchase #2	$176.95	3.414%	$182.9911	$182.99	$183.00	$183.00
Purchase #3	$197.32	3.691%	$204.6031	$204.60	$204.60	$204.60
Purchase #4	$148.82	7.579%	$160.0991	$160.10	$160.10	$160.10
Purchase #5	$59.60	8.858%	$64.8794	$64.88	$64.90	$64.90
Purchase #6	$167.48	10.723%	$185.4389	$185.44	$185.45	$185.40
Purchase #7	$29.93	5.593%	$31.604	$31.60	$31.60	$31.60
7 purchase totals =	$1,025.73		$1,086.5077	$1,086.50	$1,086.55	$1,086.50