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	$114.29	7.712%	$123.104	$123.10	$123.10	$123.10
Purchase #2	$31.82	5.674%	$33.6255	$33.63	$33.65	$33.60
Purchase #3	$90.45	13.527%	$102.6852	$102.69	$102.70	$102.70
Purchase #4	$244.51	9.291%	$267.2274	$267.23	$267.25	$267.20
Purchase #5	$163.43	11.600%	$182.3879	$182.39	$182.40	$182.40
Purchase #6	$25.95	7.492%	$27.8942	$27.89	$27.90	$27.90
Purchase #7	$160.93	5.714%	$170.1255	$170.13	$170.15	$170.10
7 purchase totals =	$831.38		$907.0497	$907.06	$907.15	$907.00