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	$216.57	9.192%	$236.4771	$236.48	$236.50	$236.50
Purchase #2	$42.44	9.285%	$46.3806	$46.38	$46.40	$46.40
Purchase #3	$163.68	9.336%	$178.9612	$178.96	$178.95	$179.00
Purchase #4	$189.66	5.625%	$200.3284	$200.33	$200.35	$200.30
Purchase #5	$49.91	7.277%	$53.542	$53.54	$53.55	$53.50
Purchase #6	$123.98	11.119%	$137.7653	$137.77	$137.75	$137.80
Purchase #7	$72.33	4.282%	$75.4272	$75.43	$75.45	$75.40
7 purchase totals =	$858.57		$928.8818	$928.89	$928.95	$928.90