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	$232.87	13.840%	$265.0992	$265.10	$265.10	$265.10
Purchase #2	$120.56	4.833%	$126.3867	$126.39	$126.40	$126.40
Purchase #3	$202.37	13.249%	$229.182	$229.18	$229.20	$229.20
Purchase #4	$157.53	9.432%	$172.3882	$172.39	$172.40	$172.40
Purchase #5	$141.87	10.410%	$156.6387	$156.64	$156.65	$156.60
Purchase #6	$76.42	6.194%	$81.1535	$81.15	$81.15	$81.20
Purchase #7	$43.83	4.655%	$45.8703	$45.87	$45.85	$45.90
7 purchase totals =	$975.45		$1,076.7186	$1,076.72	$1,076.75	$1,076.80