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	$17.60	4.369%	$18.3689	$18.37	$18.35	$18.40
Purchase #2	$150.27	4.799%	$157.4815	$157.48	$157.50	$157.50
Purchase #3	$174.43	4.458%	$182.2061	$182.21	$182.20	$182.20
Purchase #4	$76.42	8.291%	$82.756	$82.76	$82.75	$82.80
Purchase #5	$91.62	12.329%	$102.9158	$102.92	$102.90	$102.90
Purchase #6	$245.53	3.619%	$254.4157	$254.42	$254.40	$254.40
Purchase #7	$112.34	13.597%	$127.6149	$127.61	$127.60	$127.60
7 purchase totals =	$868.21		$925.7589	$925.77	$925.70	$925.80