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	$110.75	6.757%	$118.2334	$118.23	$118.25	$118.20
Purchase #2	$152.93	12.819%	$172.5341	$172.53	$172.55	$172.50
Purchase #3	$109.40	13.274%	$123.9218	$123.92	$123.90	$123.90
Purchase #4	$109.45	5.397%	$115.357	$115.36	$115.35	$115.40
Purchase #5	$66.64	9.171%	$72.7516	$72.75	$72.75	$72.80
Purchase #6	$218.37	11.714%	$243.9499	$243.95	$243.95	$243.90
Purchase #7	$179.52	5.762%	$189.8639	$189.86	$189.85	$189.90
7 purchase totals =	$947.06		$1,036.6117	$1,036.60	$1,036.60	$1,036.60