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	$198.67	9.418%	$217.3807	$217.38	$217.40	$217.40
Purchase #2	$89.59	12.206%	$100.5254	$100.53	$100.55	$100.50
Purchase #3	$45.96	10.602%	$50.8327	$50.83	$50.85	$50.80
Purchase #4	$113.55	8.688%	$123.4152	$123.42	$123.40	$123.40
Purchase #5	$98.60	12.812%	$111.2326	$111.23	$111.25	$111.20
Purchase #6	$231.83	7.519%	$249.2613	$249.26	$249.25	$249.30
Purchase #7	$171.47	4.424%	$179.0558	$179.06	$179.05	$179.10
7 purchase totals =	$949.67		$1,031.7037	$1,031.71	$1,031.75	$1,031.70