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	$38.54	12.609%	$43.3995	$43.40	$43.40	$43.40
Purchase #2	$173.69	6.834%	$185.56	$185.56	$185.55	$185.60
Purchase #3	$248.27	7.333%	$266.4756	$266.48	$266.50	$266.50
Purchase #4	$171.62	7.813%	$185.0287	$185.03	$185.05	$185.00
Purchase #5	$227.67	6.558%	$242.6006	$242.60	$242.60	$242.60
Purchase #6	$163.88	5.238%	$172.464	$172.46	$172.45	$172.50
Purchase #7	$53.73	12.388%	$60.3861	$60.39	$60.40	$60.40
7 purchase totals =	$1,077.40		$1,155.9145	$1,155.92	$1,155.95	$1,156.00