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	$181.42	9.197%	$198.1052	$198.11	$198.10	$198.10
Purchase #2	$163.66	13.538%	$185.8163	$185.82	$185.80	$185.80
Purchase #3	$101.55	9.604%	$111.3029	$111.30	$111.30	$111.30
Purchase #4	$31.89	11.257%	$35.4799	$35.48	$35.50	$35.50
Purchase #5	$174.59	4.548%	$182.5304	$182.53	$182.55	$182.50
Purchase #6	$75.87	3.647%	$78.637	$78.64	$78.65	$78.60
Purchase #7	$107.26	8.752%	$116.6474	$116.65	$116.65	$116.60
7 purchase totals =	$836.24		$908.5191	$908.53	$908.55	$908.40