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	$90.77	13.317%	$102.8578	$102.86	$102.85	$102.90
Purchase #2	$10.33	5.835%	$10.9328	$10.93	$10.95	$10.90
Purchase #3	$84.66	3.411%	$87.5478	$87.55	$87.55	$87.50
Purchase #4	$38.43	3.662%	$39.8373	$39.84	$39.85	$39.80
Purchase #5	$67.86	7.430%	$72.902	$72.90	$72.90	$72.90
Purchase #6	$157.36	10.618%	$174.0685	$174.07	$174.05	$174.10
Purchase #7	$37.71	13.767%	$42.9015	$42.90	$42.90	$42.90
7 purchase totals =	$487.12		$531.0477	$531.05	$531.05	$531.00