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	$32.45	10.345%	$35.807	$35.81	$35.80	$35.80
Purchase #2	$189.81	3.573%	$196.5919	$196.59	$196.60	$196.60
Purchase #3	$79.45	6.780%	$84.8367	$84.84	$84.85	$84.80
Purchase #4	$220.58	5.851%	$233.4861	$233.49	$233.50	$233.50
Purchase #5	$223.30	3.844%	$231.8837	$231.88	$231.90	$231.90
Purchase #6	$47.78	9.712%	$52.4204	$52.42	$52.40	$52.40
Purchase #7	$193.29	9.313%	$211.2911	$211.29	$211.30	$211.30
7 purchase totals =	$986.66		$1,046.3169	$1,046.32	$1,046.35	$1,046.30