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	$178.48	4.375%	$186.2885	$186.29	$186.30	$186.30
Purchase #2	$221.80	7.498%	$238.4306	$238.43	$238.45	$238.40
Purchase #3	$250.26	4.671%	$261.9496	$261.95	$261.95	$261.90
Purchase #4	$187.25	11.412%	$208.619	$208.62	$208.60	$208.60
Purchase #5	$127.49	11.342%	$141.9499	$141.95	$141.95	$141.90
Purchase #6	$169.71	10.141%	$186.9203	$186.92	$186.90	$186.90
Purchase #7	$37.25	4.391%	$38.8856	$38.89	$38.90	$38.90
7 purchase totals =	$1,172.24		$1,263.0435	$1,263.05	$1,263.05	$1,262.90