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	$140.40	10.332%	$154.9061	$154.91	$154.90	$154.90
Purchase #2	$161.66	5.121%	$169.9386	$169.94	$169.95	$169.90
Purchase #3	$37.83	13.144%	$42.8024	$42.80	$42.80	$42.80
Purchase #4	$29.55	13.627%	$33.5768	$33.58	$33.60	$33.60
Purchase #5	$42.39	11.141%	$47.1127	$47.11	$47.10	$47.10
Purchase #6	$161.77	7.442%	$173.8089	$173.81	$173.80	$173.80
Purchase #7	$31.64	7.285%	$33.945	$33.95	$33.95	$33.90
7 purchase totals =	$605.24		$656.0905	$656.10	$656.10	$656.00