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	$151.86	7.295%	$162.9382	$162.94	$162.95	$162.90
Purchase #2	$151.69	8.379%	$164.4001	$164.40	$164.40	$164.40
Purchase #3	$18.48	5.729%	$19.5387	$19.54	$19.55	$19.50
Purchase #4	$34.61	3.635%	$35.8681	$35.87	$35.85	$35.90
Purchase #5	$209.63	11.592%	$233.9303	$233.93	$233.95	$233.90
Purchase #6	$236.38	12.297%	$265.4476	$265.45	$265.45	$265.40
Purchase #7	$140.96	12.283%	$158.2741	$158.27	$158.25	$158.30
7 purchase totals =	$943.61		$1,040.3971	$1,040.40	$1,040.40	$1,040.30