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	$90.91	4.179%	$94.7091	$94.71	$94.70	$94.70
Purchase #2	$196.49	13.798%	$223.6017	$223.60	$223.60	$223.60
Purchase #3	$48.71	11.398%	$54.262	$54.26	$54.25	$54.30
Purchase #4	$85.54	11.533%	$95.4053	$95.41	$95.40	$95.40
Purchase #5	$206.97	11.577%	$230.9309	$230.93	$230.95	$230.90
Purchase #6	$199.58	7.864%	$215.275	$215.28	$215.30	$215.30
Purchase #7	$17.48	7.513%	$18.7933	$18.79	$18.80	$18.80
7 purchase totals =	$845.68		$932.9773	$932.98	$933.00	$933.00