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	$191.34	4.469%	$199.891	$199.89	$199.90	$199.90
Purchase #2	$204.94	10.115%	$225.6697	$225.67	$225.65	$225.70
Purchase #3	$92.47	11.238%	$102.8618	$102.86	$102.85	$102.90
Purchase #4	$150.58	10.462%	$166.3337	$166.33	$166.35	$166.30
Purchase #5	$157.32	3.804%	$163.3045	$163.30	$163.30	$163.30
Purchase #6	$70.93	10.596%	$78.4457	$78.45	$78.45	$78.40
Purchase #7	$156.29	6.694%	$166.7521	$166.75	$166.75	$166.80
7 purchase totals =	$1,023.87		$1,103.2585	$1,103.25	$1,103.25	$1,103.30