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	$43.60	5.212%	$45.8724	$45.87	$45.85	$45.90
Purchase #2	$31.49	6.477%	$33.5296	$33.53	$33.55	$33.50
Purchase #3	$237.74	8.866%	$258.818	$258.82	$258.80	$258.80
Purchase #4	$79.84	12.107%	$89.5062	$89.51	$89.50	$89.50
Purchase #5	$40.84	5.387%	$43.0401	$43.04	$43.05	$43.00
Purchase #6	$228.77	4.310%	$238.63	$238.63	$238.65	$238.60
Purchase #7	$166.26	12.178%	$186.5071	$186.51	$186.50	$186.50
7 purchase totals =	$828.54		$895.9034	$895.91	$895.90	$895.80