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	$135.59	11.204%	$150.7815	$150.78	$150.80	$150.80
Purchase #2	$119.89	12.547%	$134.9326	$134.93	$134.95	$134.90
Purchase #3	$142.26	6.511%	$151.5225	$151.52	$151.50	$151.50
Purchase #4	$231.93	4.429%	$242.2022	$242.20	$242.20	$242.20
Purchase #5	$36.74	9.256%	$40.1407	$40.14	$40.15	$40.10
Purchase #6	$228.69	5.726%	$241.7848	$241.78	$241.80	$241.80
Purchase #7	$215.79	3.459%	$223.2542	$223.25	$223.25	$223.30
7 purchase totals =	$1,110.89		$1,184.6185	$1,184.60	$1,184.65	$1,184.60