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	$146.31	6.574%	$155.9284	$155.93	$155.95	$155.90
Purchase #2	$248.88	9.836%	$273.3598	$273.36	$273.35	$273.40
Purchase #3	$158.52	13.260%	$179.5398	$179.54	$179.55	$179.50
Purchase #4	$65.96	7.752%	$71.0732	$71.07	$71.05	$71.10
Purchase #5	$53.27	8.693%	$57.9008	$57.90	$57.90	$57.90
Purchase #6	$189.27	5.436%	$199.5587	$199.56	$199.55	$199.60
Purchase #7	$125.89	9.373%	$137.6897	$137.69	$137.70	$137.70
7 purchase totals =	$988.10		$1,075.0504	$1,075.05	$1,075.05	$1,075.10