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	$103.66	8.610%	$112.5851	$112.59	$112.60	$112.60
Purchase #2	$62.34	4.258%	$64.9944	$64.99	$65.00	$65.00
Purchase #3	$120.64	8.722%	$131.1622	$131.16	$131.15	$131.20
Purchase #4	$40.71	7.848%	$43.9049	$43.90	$43.90	$43.90
Purchase #5	$172.53	10.614%	$190.8423	$190.84	$190.85	$190.80
Purchase #6	$56.83	8.399%	$61.6032	$61.60	$61.60	$61.60
Purchase #7	$233.57	11.287%	$259.933	$259.93	$259.95	$259.90
7 purchase totals =	$790.28		$865.0251	$865.01	$865.05	$865.00