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	$77.99	11.588%	$87.0275	$87.03	$87.05	$87.00
Purchase #2	$211.44	5.106%	$222.2361	$222.24	$222.25	$222.20
Purchase #3	$86.65	4.364%	$90.4314	$90.43	$90.45	$90.40
Purchase #4	$190.54	3.106%	$196.4582	$196.46	$196.45	$196.50
Purchase #5	$232.87	4.389%	$243.0907	$243.09	$243.10	$243.10
Purchase #6	$36.80	5.182%	$38.707	$38.71	$38.70	$38.70
Purchase #7	$146.43	7.689%	$157.689	$157.69	$157.70	$157.70
7 purchase totals =	$982.72		$1,035.6399	$1,035.65	$1,035.70	$1,035.60