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	$43.66	7.314%	$46.8533	$46.85	$46.85	$46.90
Purchase #2	$48.83	8.600%	$53.0294	$53.03	$53.05	$53.00
Purchase #3	$40.48	8.351%	$43.8605	$43.86	$43.85	$43.90
Purchase #4	$67.57	6.623%	$72.0452	$72.05	$72.05	$72.00
Purchase #5	$211.41	13.136%	$239.1808	$239.18	$239.20	$239.20
Purchase #6	$94.50	7.677%	$101.7548	$101.75	$101.75	$101.80
Purchase #7	$248.82	3.221%	$256.8345	$256.83	$256.85	$256.80
7 purchase totals =	$755.27		$813.5585	$813.55	$813.60	$813.60