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	$50.79	5.240%	$53.4514	$53.45	$53.45	$53.50
Purchase #2	$12.88	7.211%	$13.8088	$13.81	$13.80	$13.80
Purchase #3	$227.46	6.803%	$242.9341	$242.93	$242.95	$242.90
Purchase #4	$91.53	7.868%	$98.7316	$98.73	$98.75	$98.70
Purchase #5	$38.69	4.580%	$40.462	$40.46	$40.45	$40.50
Purchase #6	$43.93	13.578%	$49.8948	$49.89	$49.90	$49.90
Purchase #7	$168.25	13.405%	$190.8039	$190.80	$190.80	$190.80
7 purchase totals =	$633.53		$690.0866	$690.07	$690.10	$690.10