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	$135.50	9.142%	$147.8874	$147.89	$147.90	$147.90
Purchase #2	$64.91	9.852%	$71.3049	$71.30	$71.30	$71.30
Purchase #3	$44.87	13.666%	$51.0019	$51.00	$51.00	$51.00
Purchase #4	$113.83	8.417%	$123.4111	$123.41	$123.40	$123.40
Purchase #5	$182.68	12.704%	$205.8877	$205.89	$205.90	$205.90
Purchase #6	$177.33	3.142%	$182.9017	$182.90	$182.90	$182.90
Purchase #7	$70.71	9.677%	$77.5526	$77.55	$77.55	$77.60
7 purchase totals =	$789.83		$859.9473	$859.94	$859.95	$860.00