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	$161.83	5.270%	$170.3584	$170.36	$170.35	$170.40
Purchase #2	$40.65	12.826%	$45.8638	$45.86	$45.85	$45.90
Purchase #3	$209.57	8.808%	$228.0289	$228.03	$228.05	$228.00
Purchase #4	$109.72	5.240%	$115.4693	$115.47	$115.45	$115.50
Purchase #5	$162.95	10.596%	$180.2162	$180.22	$180.20	$180.20
Purchase #6	$183.40	4.776%	$192.1592	$192.16	$192.15	$192.20
Purchase #7	$78.80	8.186%	$85.2506	$85.25	$85.25	$85.30
7 purchase totals =	$946.92		$1,017.3464	$1,017.35	$1,017.30	$1,017.50