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	$186.32	10.518%	$205.9171	$205.92	$205.90	$205.90
Purchase #2	$130.34	9.600%	$142.8526	$142.85	$142.85	$142.90
Purchase #3	$189.37	4.854%	$198.562	$198.56	$198.55	$198.60
Purchase #4	$135.49	5.195%	$142.5287	$142.53	$142.55	$142.50
Purchase #5	$235.34	12.190%	$264.0279	$264.03	$264.05	$264.00
Purchase #6	$74.80	5.437%	$78.8669	$78.87	$78.85	$78.90
Purchase #7	$215.94	4.558%	$225.7825	$225.78	$225.80	$225.80
7 purchase totals =	$1,167.60		$1,258.5377	$1,258.54	$1,258.55	$1,258.60