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	$63.90	11.256%	$71.0926	$71.09	$71.10	$71.10
Purchase #2	$226.85	13.507%	$257.4906	$257.49	$257.50	$257.50
Purchase #3	$219.78	7.870%	$237.0767	$237.08	$237.10	$237.10
Purchase #4	$114.63	11.550%	$127.8698	$127.87	$127.85	$127.90
Purchase #5	$96.76	3.839%	$100.4746	$100.47	$100.45	$100.50
Purchase #6	$138.66	4.257%	$144.5628	$144.56	$144.55	$144.60
Purchase #7	$157.53	6.791%	$168.2279	$168.23	$168.25	$168.20
7 purchase totals =	$1,018.11		$1,106.7950	$1,106.79	$1,106.80	$1,106.90