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	$87.34	9.298%	$95.4609	$95.46	$95.45	$95.50
Purchase #2	$173.55	13.186%	$196.4343	$196.43	$196.45	$196.40
Purchase #3	$43.97	8.672%	$47.7831	$47.78	$47.80	$47.80
Purchase #4	$94.45	9.149%	$103.0912	$103.09	$103.10	$103.10
Purchase #5	$38.77	11.294%	$43.1487	$43.15	$43.15	$43.10
Purchase #6	$36.91	11.215%	$41.0495	$41.05	$41.05	$41.00
Purchase #7	$248.69	6.334%	$264.442	$264.44	$264.45	$264.40
7 purchase totals =	$723.68		$791.4097	$791.40	$791.45	$791.30