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	$38.59	5.267%	$40.6225	$40.62	$40.60	$40.60
Purchase #2	$131.98	10.287%	$145.5568	$145.56	$145.55	$145.60
Purchase #3	$45.82	7.822%	$49.404	$49.40	$49.40	$49.40
Purchase #4	$123.86	5.400%	$130.5484	$130.55	$130.55	$130.50
Purchase #5	$236.94	7.778%	$255.3692	$255.37	$255.35	$255.40
Purchase #6	$234.25	4.600%	$245.0255	$245.03	$245.05	$245.00
Purchase #7	$212.84	11.591%	$237.5103	$237.51	$237.50	$237.50
7 purchase totals =	$1,024.28		$1,104.0367	$1,104.04	$1,104.00	$1,104.00