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	$72.78	11.380%	$81.0624	$81.06	$81.05	$81.10
Purchase #2	$240.85	5.778%	$254.7663	$254.77	$254.75	$254.80
Purchase #3	$96.49	4.599%	$100.9276	$100.93	$100.95	$100.90
Purchase #4	$178.77	13.828%	$203.4903	$203.49	$203.50	$203.50
Purchase #5	$80.71	9.866%	$88.6728	$88.67	$88.65	$88.70
Purchase #6	$185.38	11.292%	$206.3131	$206.31	$206.30	$206.30
Purchase #7	$162.47	10.724%	$179.8933	$179.89	$179.90	$179.90
7 purchase totals =	$1,017.45		$1,115.1258	$1,115.12	$1,115.10	$1,115.20