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	$54.46	9.338%	$59.5455	$59.55	$59.55	$59.50
Purchase #2	$34.97	13.423%	$39.664	$39.66	$39.65	$39.70
Purchase #3	$102.85	9.658%	$112.7833	$112.78	$112.80	$112.80
Purchase #4	$37.30	9.474%	$40.8338	$40.83	$40.85	$40.80
Purchase #5	$142.51	6.649%	$151.9855	$151.99	$152.00	$152.00
Purchase #6	$13.43	10.812%	$14.8821	$14.88	$14.90	$14.90
Purchase #7	$49.46	3.645%	$51.2628	$51.26	$51.25	$51.30
7 purchase totals =	$434.98		$470.9570	$470.95	$471.00	$471.00