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	$35.43	4.311%	$36.9574	$36.96	$36.95	$37.00
Purchase #2	$29.66	9.234%	$32.3988	$32.40	$32.40	$32.40
Purchase #3	$78.66	13.214%	$89.0541	$89.05	$89.05	$89.10
Purchase #4	$36.58	11.770%	$40.8855	$40.89	$40.90	$40.90
Purchase #5	$11.54	5.219%	$12.1423	$12.14	$12.15	$12.10
Purchase #6	$78.82	6.762%	$84.1498	$84.15	$84.15	$84.10
Purchase #7	$242.55	7.769%	$261.3937	$261.39	$261.40	$261.40
7 purchase totals =	$513.24		$556.9816	$556.98	$557.00	$557.00