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	$101.26	3.334%	$104.636	$104.64	$104.65	$104.60
Purchase #2	$209.36	13.484%	$237.5901	$237.59	$237.60	$237.60
Purchase #3	$14.40	10.731%	$15.9453	$15.95	$15.95	$15.90
Purchase #4	$80.64	11.518%	$89.9281	$89.93	$89.95	$89.90
Purchase #5	$78.38	13.576%	$89.0209	$89.02	$89.00	$89.00
Purchase #6	$147.40	4.452%	$153.9622	$153.96	$153.95	$154.00
Purchase #7	$12.94	13.353%	$14.6679	$14.67	$14.65	$14.70
7 purchase totals =	$644.38		$705.7505	$705.76	$705.75	$705.70