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	$223.84	13.867%	$254.8799	$254.88	$254.90	$254.90
Purchase #2	$12.83	5.766%	$13.5698	$13.57	$13.55	$13.60
Purchase #3	$172.74	12.530%	$194.3843	$194.38	$194.40	$194.40
Purchase #4	$51.73	4.576%	$54.0972	$54.10	$54.10	$54.10
Purchase #5	$34.66	3.651%	$35.9254	$35.93	$35.95	$35.90
Purchase #6	$54.45	9.869%	$59.8237	$59.82	$59.80	$59.80
Purchase #7	$142.25	3.825%	$147.6911	$147.69	$147.70	$147.70
7 purchase totals =	$692.50		$760.3714	$760.37	$760.40	$760.40