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	$29.51	11.487%	$32.8998	$32.90	$32.90	$32.90
Purchase #2	$51.58	7.694%	$55.5486	$55.55	$55.55	$55.50
Purchase #3	$6.31	4.870%	$6.6173	$6.62	$6.60	$6.60
Purchase #4	$205.95	5.841%	$217.9795	$217.98	$218.00	$218.00
Purchase #5	$214.65	4.166%	$223.5923	$223.59	$223.60	$223.60
Purchase #6	$13.82	5.723%	$14.6109	$14.61	$14.60	$14.60
Purchase #7	$238.77	11.252%	$265.6364	$265.64	$265.65	$265.60
7 purchase totals =	$760.59		$816.8848	$816.89	$816.90	$816.80