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	$151.34	7.123%	$162.1199	$162.12	$162.10	$162.10
Purchase #2	$248.42	12.842%	$280.3221	$280.32	$280.30	$280.30
Purchase #3	$93.42	7.791%	$100.6984	$100.70	$100.70	$100.70
Purchase #4	$247.71	5.596%	$261.5719	$261.57	$261.55	$261.60
Purchase #5	$26.79	11.377%	$29.8379	$29.84	$29.85	$29.80
Purchase #6	$51.59	5.850%	$54.608	$54.61	$54.60	$54.60
Purchase #7	$26.87	11.263%	$29.8964	$29.90	$29.90	$29.90
7 purchase totals =	$846.14		$919.0546	$919.06	$919.00	$919.00