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	$74.94	9.651%	$82.1725	$82.17	$82.15	$82.20
Purchase #2	$172.72	5.861%	$182.8431	$182.84	$182.85	$182.80
Purchase #3	$213.81	9.623%	$234.3849	$234.38	$234.40	$234.40
Purchase #4	$174.66	6.215%	$185.5151	$185.52	$185.50	$185.50
Purchase #5	$115.52	12.270%	$129.6943	$129.69	$129.70	$129.70
Purchase #6	$98.92	6.872%	$105.7178	$105.72	$105.70	$105.70
Purchase #7	$12.55	5.620%	$13.2553	$13.26	$13.25	$13.30
7 purchase totals =	$863.12		$933.5830	$933.58	$933.55	$933.60