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	$78.31	4.795%	$82.065	$82.07	$82.05	$82.10
Purchase #2	$146.43	3.158%	$151.0543	$151.05	$151.05	$151.10
Purchase #3	$72.25	3.674%	$74.9045	$74.90	$74.90	$74.90
Purchase #4	$150.52	3.497%	$155.7837	$155.78	$155.80	$155.80
Purchase #5	$114.82	3.770%	$119.1487	$119.15	$119.15	$119.10
Purchase #6	$92.34	12.616%	$103.9896	$103.99	$104.00	$104.00
Purchase #7	$38.36	13.693%	$43.6126	$43.61	$43.60	$43.60
7 purchase totals =	$693.03		$730.5584	$730.55	$730.55	$730.60