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	$115.44	10.162%	$127.171	$127.17	$127.15	$127.20
Purchase #2	$201.49	4.365%	$210.285	$210.29	$210.30	$210.30
Purchase #3	$64.86	7.316%	$69.6052	$69.61	$69.60	$69.60
Purchase #4	$209.43	5.477%	$220.9005	$220.90	$220.90	$220.90
Purchase #5	$153.97	11.510%	$171.6919	$171.69	$171.70	$171.70
Purchase #6	$133.49	4.538%	$139.5478	$139.55	$139.55	$139.50
Purchase #7	$212.99	9.720%	$233.6926	$233.69	$233.70	$233.70
7 purchase totals =	$1,091.67		$1,172.8940	$1,172.90	$1,172.90	$1,172.90