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	$180.83	10.754%	$200.2765	$200.28	$200.30	$200.30
Purchase #2	$75.76	3.633%	$78.5124	$78.51	$78.50	$78.50
Purchase #3	$120.62	9.440%	$132.0065	$132.01	$132.00	$132.00
Purchase #4	$171.88	3.217%	$177.4094	$177.41	$177.40	$177.40
Purchase #5	$125.35	13.376%	$142.1168	$142.12	$142.10	$142.10
Purchase #6	$218.90	12.323%	$245.875	$245.88	$245.90	$245.90
Purchase #7	$133.76	12.438%	$150.3971	$150.40	$150.40	$150.40
7 purchase totals =	$1,027.10		$1,126.5937	$1,126.61	$1,126.60	$1,126.60