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	$168.78	8.186%	$182.5963	$182.60	$182.60	$182.60
Purchase #2	$104.58	5.591%	$110.4271	$110.43	$110.45	$110.40
Purchase #3	$18.25	8.650%	$19.8286	$19.83	$19.85	$19.80
Purchase #4	$97.84	13.847%	$111.3879	$111.39	$111.40	$111.40
Purchase #5	$191.76	8.848%	$208.7269	$208.73	$208.75	$208.70
Purchase #6	$92.80	8.554%	$100.7381	$100.74	$100.75	$100.70
Purchase #7	$249.66	8.276%	$270.3219	$270.32	$270.30	$270.30
7 purchase totals =	$923.67		$1,004.0268	$1,004.04	$1,004.10	$1,003.90