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	$156.82	6.699%	$167.3254	$167.33	$167.35	$167.30
Purchase #2	$208.38	6.534%	$221.9955	$222.00	$222.00	$222.00
Purchase #3	$48.74	6.544%	$51.9295	$51.93	$51.95	$51.90
Purchase #4	$72.40	7.790%	$78.04	$78.04	$78.05	$78.00
Purchase #5	$38.78	10.454%	$42.8341	$42.83	$42.85	$42.80
Purchase #6	$145.31	7.710%	$156.5134	$156.51	$156.50	$156.50
Purchase #7	$123.94	9.371%	$135.5544	$135.55	$135.55	$135.60
7 purchase totals =	$794.37		$854.1923	$854.19	$854.25	$854.10