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	$56.80	4.308%	$59.2469	$59.25	$59.25	$59.20
Purchase #2	$50.43	5.396%	$53.1512	$53.15	$53.15	$53.20
Purchase #3	$161.46	6.208%	$171.4834	$171.48	$171.50	$171.50
Purchase #4	$94.66	3.610%	$98.0772	$98.08	$98.10	$98.10
Purchase #5	$33.42	6.692%	$35.6565	$35.66	$35.65	$35.70
Purchase #6	$14.83	6.272%	$15.7601	$15.76	$15.75	$15.80
Purchase #7	$54.68	3.294%	$56.4812	$56.48	$56.50	$56.50
7 purchase totals =	$466.28		$489.8565	$489.86	$489.90	$490.00