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	$97.48	6.666%	$103.978	$103.98	$104.00	$104.00
Purchase #2	$208.89	6.307%	$222.0647	$222.06	$222.05	$222.10
Purchase #3	$37.51	12.289%	$42.1196	$42.12	$42.10	$42.10
Purchase #4	$71.54	13.226%	$81.0019	$81.00	$81.00	$81.00
Purchase #5	$218.95	8.139%	$236.7703	$236.77	$236.75	$236.80
Purchase #6	$228.89	3.433%	$236.7478	$236.75	$236.75	$236.70
Purchase #7	$135.51	12.296%	$152.1723	$152.17	$152.15	$152.20
7 purchase totals =	$998.77		$1,074.8546	$1,074.85	$1,074.80	$1,074.90