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	$71.89	8.806%	$78.2206	$78.22	$78.20	$78.20
Purchase #2	$136.62	4.130%	$142.2624	$142.26	$142.25	$142.30
Purchase #3	$119.81	4.715%	$125.459	$125.46	$125.45	$125.50
Purchase #4	$203.25	11.659%	$226.9469	$226.95	$226.95	$226.90
Purchase #5	$103.78	10.415%	$114.5887	$114.59	$114.60	$114.60
Purchase #6	$125.77	3.753%	$130.4901	$130.49	$130.50	$130.50
Purchase #7	$183.26	8.490%	$198.8188	$198.82	$198.80	$198.80
7 purchase totals =	$944.38		$1,016.7865	$1,016.79	$1,016.75	$1,016.80