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	$85.81	11.872%	$95.9974	$96.00	$96.00	$96.00
Purchase #2	$35.68	3.524%	$36.9374	$36.94	$36.95	$36.90
Purchase #3	$37.93	10.139%	$41.7757	$41.78	$41.80	$41.80
Purchase #4	$54.35	9.592%	$59.5633	$59.56	$59.55	$59.60
Purchase #5	$190.28	7.691%	$204.9144	$204.91	$204.90	$204.90
Purchase #6	$14.55	6.707%	$15.5259	$15.53	$15.55	$15.50
Purchase #7	$170.85	9.161%	$186.5016	$186.50	$186.50	$186.50
7 purchase totals =	$589.45		$641.2157	$641.22	$641.25	$641.20