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	$31.60	12.834%	$35.6555	$35.66	$35.65	$35.70
Purchase #2	$205.99	8.127%	$222.7308	$222.73	$222.75	$222.70
Purchase #3	$158.80	5.465%	$167.4784	$167.48	$167.50	$167.50
Purchase #4	$35.29	11.192%	$39.2397	$39.24	$39.25	$39.20
Purchase #5	$185.74	13.353%	$210.5419	$210.54	$210.55	$210.50
Purchase #6	$184.93	11.110%	$205.4757	$205.48	$205.50	$205.50
Purchase #7	$93.38	3.142%	$96.314	$96.31	$96.30	$96.30
7 purchase totals =	$895.73		$977.4360	$977.44	$977.50	$977.40