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	$155.65	7.844%	$167.8592	$167.86	$167.85	$167.90
Purchase #2	$10.29	5.679%	$10.8744	$10.87	$10.85	$10.90
Purchase #3	$49.77	5.236%	$52.376	$52.38	$52.40	$52.40
Purchase #4	$184.50	6.132%	$195.8135	$195.81	$195.80	$195.80
Purchase #5	$132.43	8.534%	$143.7316	$143.73	$143.75	$143.70
Purchase #6	$59.71	3.860%	$62.0148	$62.01	$62.00	$62.00
Purchase #7	$32.86	7.451%	$35.3084	$35.31	$35.30	$35.30
7 purchase totals =	$625.21		$667.9779	$667.97	$667.95	$668.00