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	$193.66	10.443%	$213.8839	$213.88	$213.90	$213.90
Purchase #2	$89.88	7.338%	$96.4754	$96.48	$96.50	$96.50
Purchase #3	$249.27	13.787%	$283.6369	$283.64	$283.65	$283.60
Purchase #4	$185.37	12.671%	$208.8582	$208.86	$208.85	$208.90
Purchase #5	$27.80	13.456%	$31.5408	$31.54	$31.55	$31.50
Purchase #6	$38.55	4.214%	$40.1745	$40.17	$40.15	$40.20
Purchase #7	$174.87	13.458%	$198.404	$198.40	$198.40	$198.40
7 purchase totals =	$959.40		$1,072.9737	$1,072.97	$1,073.00	$1,073.00