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	$171.46	4.656%	$179.4432	$179.44	$179.45	$179.40
Purchase #2	$82.90	7.821%	$89.3836	$89.38	$89.40	$89.40
Purchase #3	$8.92	11.783%	$9.971	$9.97	$9.95	$10.00
Purchase #4	$184.68	3.130%	$190.4605	$190.46	$190.45	$190.50
Purchase #5	$193.53	5.114%	$203.4271	$203.43	$203.45	$203.40
Purchase #6	$121.74	4.724%	$127.491	$127.49	$127.50	$127.50
Purchase #7	$174.52	3.429%	$180.5043	$180.50	$180.50	$180.50
7 purchase totals =	$937.75		$980.6807	$980.67	$980.70	$980.70