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	$34.30	3.422%	$35.4737	$35.47	$35.45	$35.50
Purchase #2	$211.43	4.770%	$221.5152	$221.52	$221.50	$221.50
Purchase #3	$22.56	13.238%	$25.5465	$25.55	$25.55	$25.50
Purchase #4	$88.43	9.755%	$97.0563	$97.06	$97.05	$97.10
Purchase #5	$186.89	10.176%	$205.9079	$205.91	$205.90	$205.90
Purchase #6	$172.41	6.710%	$183.9787	$183.98	$184.00	$184.00
Purchase #7	$127.76	12.662%	$143.937	$143.94	$143.95	$143.90
7 purchase totals =	$843.78		$913.4153	$913.43	$913.40	$913.40