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	$89.43	3.476%	$92.5386	$92.54	$92.55	$92.50
Purchase #2	$231.77	3.416%	$239.6873	$239.69	$239.70	$239.70
Purchase #3	$200.53	6.254%	$213.0711	$213.07	$213.05	$213.10
Purchase #4	$54.69	5.849%	$57.8888	$57.89	$57.90	$57.90
Purchase #5	$51.34	5.179%	$53.9989	$54.00	$54.00	$54.00
Purchase #6	$159.71	8.158%	$172.7391	$172.74	$172.75	$172.70
Purchase #7	$159.84	12.145%	$179.2526	$179.25	$179.25	$179.30
7 purchase totals =	$947.31		$1,009.1764	$1,009.18	$1,009.20	$1,009.20