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	$105.83	7.768%	$114.0509	$114.05	$114.05	$114.10
Purchase #2	$78.33	5.221%	$82.4196	$82.42	$82.40	$82.40
Purchase #3	$129.50	13.437%	$146.9009	$146.90	$146.90	$146.90
Purchase #4	$83.80	3.706%	$86.9056	$86.91	$86.90	$86.90
Purchase #5	$144.52	5.305%	$152.1868	$152.19	$152.20	$152.20
Purchase #6	$63.45	13.610%	$72.0855	$72.09	$72.10	$72.10
Purchase #7	$75.78	3.252%	$78.2444	$78.24	$78.25	$78.20
7 purchase totals =	$681.21		$732.7937	$732.80	$732.80	$732.80