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	$183.70	9.105%	$200.4259	$200.43	$200.45	$200.40
Purchase #2	$75.44	8.106%	$81.5552	$81.56	$81.55	$81.60
Purchase #3	$243.96	7.494%	$262.2424	$262.24	$262.25	$262.20
Purchase #4	$179.64	9.189%	$196.1471	$196.15	$196.15	$196.10
Purchase #5	$64.37	12.637%	$72.5044	$72.50	$72.50	$72.50
Purchase #6	$5.98	6.464%	$6.3665	$6.37	$6.35	$6.40
Purchase #7	$187.74	3.420%	$194.1607	$194.16	$194.15	$194.20
7 purchase totals =	$940.83		$1,013.4022	$1,013.41	$1,013.40	$1,013.40