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	$95.57	8.696%	$103.8808	$103.88	$103.90	$103.90
Purchase #2	$45.33	12.644%	$51.0615	$51.06	$51.05	$51.10
Purchase #3	$133.81	6.727%	$142.8114	$142.81	$142.80	$142.80
Purchase #4	$95.56	4.109%	$99.4866	$99.49	$99.50	$99.50
Purchase #5	$211.45	9.447%	$231.4257	$231.43	$231.45	$231.40
Purchase #6	$212.88	6.850%	$227.4623	$227.46	$227.45	$227.50
Purchase #7	$152.78	10.696%	$169.1213	$169.12	$169.10	$169.10
7 purchase totals =	$947.38		$1,025.2496	$1,025.25	$1,025.25	$1,025.30