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	$217.35	4.626%	$227.4046	$227.40	$227.40	$227.40
Purchase #2	$130.83	8.139%	$141.4783	$141.48	$141.50	$141.50
Purchase #3	$123.92	6.755%	$132.2908	$132.29	$132.30	$132.30
Purchase #4	$8.33	3.328%	$8.6072	$8.61	$8.60	$8.60
Purchase #5	$102.73	13.277%	$116.3695	$116.37	$116.35	$116.40
Purchase #6	$196.60	13.680%	$223.4949	$223.49	$223.50	$223.50
Purchase #7	$168.26	7.405%	$180.7197	$180.72	$180.70	$180.70
7 purchase totals =	$948.02		$1,030.3650	$1,030.36	$1,030.35	$1,030.40