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	$158.79	13.264%	$179.8519	$179.85	$179.85	$179.90
Purchase #2	$16.87	11.749%	$18.8521	$18.85	$18.85	$18.90
Purchase #3	$142.99	13.525%	$162.3294	$162.33	$162.35	$162.30
Purchase #4	$102.94	11.321%	$114.5938	$114.59	$114.60	$114.60
Purchase #5	$86.49	3.644%	$89.6417	$89.64	$89.65	$89.60
Purchase #6	$90.33	8.678%	$98.1688	$98.17	$98.15	$98.20
Purchase #7	$222.98	13.451%	$252.973	$252.97	$252.95	$253.00
7 purchase totals =	$821.39		$916.4107	$916.40	$916.40	$916.50