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	$117.59	6.800%	$125.5861	$125.59	$125.60	$125.60
Purchase #2	$21.61	4.147%	$22.5062	$22.51	$22.50	$22.50
Purchase #3	$64.40	11.313%	$71.6856	$71.69	$71.70	$71.70
Purchase #4	$108.68	8.844%	$118.2917	$118.29	$118.30	$118.30
Purchase #5	$40.88	13.368%	$46.3448	$46.34	$46.35	$46.30
Purchase #6	$77.33	13.779%	$87.9853	$87.99	$88.00	$88.00
Purchase #7	$72.29	8.448%	$78.3971	$78.40	$78.40	$78.40
7 purchase totals =	$502.78		$550.7968	$550.81	$550.85	$550.80