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	$143.66	13.556%	$163.1345	$163.13	$163.15	$163.10
Purchase #2	$126.50	3.839%	$131.3563	$131.36	$131.35	$131.40
Purchase #3	$207.37	7.827%	$223.6008	$223.60	$223.60	$223.60
Purchase #4	$112.77	11.235%	$125.4397	$125.44	$125.45	$125.40
Purchase #5	$71.66	9.612%	$78.548	$78.55	$78.55	$78.50
Purchase #6	$154.26	5.267%	$162.3849	$162.38	$162.40	$162.40
Purchase #7	$185.47	3.266%	$191.5275	$191.53	$191.55	$191.50
7 purchase totals =	$1,001.69		$1,075.9917	$1,075.99	$1,076.05	$1,075.90