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	$225.62	5.433%	$237.8779	$237.88	$237.90	$237.90
Purchase #2	$187.96	10.554%	$207.7973	$207.80	$207.80	$207.80
Purchase #3	$169.39	10.668%	$187.4605	$187.46	$187.45	$187.50
Purchase #4	$6.76	12.247%	$7.5879	$7.59	$7.60	$7.60
Purchase #5	$133.82	13.797%	$152.2831	$152.28	$152.30	$152.30
Purchase #6	$249.85	12.431%	$280.9089	$280.91	$280.90	$280.90
Purchase #7	$209.67	4.260%	$218.6019	$218.60	$218.60	$218.60
7 purchase totals =	$1,183.07		$1,292.5175	$1,292.52	$1,292.55	$1,292.60