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	$50.97	7.102%	$54.5899	$54.59	$54.60	$54.60
Purchase #2	$71.86	8.278%	$77.8086	$77.81	$77.80	$77.80
Purchase #3	$19.27	7.620%	$20.7384	$20.74	$20.75	$20.70
Purchase #4	$55.77	12.596%	$62.7948	$62.79	$62.80	$62.80
Purchase #5	$235.74	12.608%	$265.4621	$265.46	$265.45	$265.50
Purchase #6	$246.48	13.819%	$280.5411	$280.54	$280.55	$280.50
Purchase #7	$155.87	7.122%	$166.9711	$166.97	$166.95	$167.00
7 purchase totals =	$835.96		$928.9060	$928.90	$928.90	$928.90