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	$177.51	4.512%	$185.5193	$185.52	$185.50	$185.50
Purchase #2	$182.86	9.381%	$200.0141	$200.01	$200.00	$200.00
Purchase #3	$171.89	3.820%	$178.4562	$178.46	$178.45	$178.50
Purchase #4	$64.90	4.386%	$67.7465	$67.75	$67.75	$67.70
Purchase #5	$180.41	5.860%	$190.982	$190.98	$191.00	$191.00
Purchase #6	$7.63	11.612%	$8.516	$8.52	$8.50	$8.50
Purchase #7	$151.92	6.192%	$161.3269	$161.33	$161.35	$161.30
7 purchase totals =	$937.12		$992.5610	$992.57	$992.55	$992.50