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	$201.89	4.293%	$210.5571	$210.56	$210.55	$210.60
Purchase #2	$130.47	11.242%	$145.1374	$145.14	$145.15	$145.10
Purchase #3	$124.67	10.133%	$137.3028	$137.30	$137.30	$137.30
Purchase #4	$155.85	5.294%	$164.1007	$164.10	$164.10	$164.10
Purchase #5	$136.95	13.656%	$155.6519	$155.65	$155.65	$155.70
Purchase #6	$126.59	5.547%	$133.6119	$133.61	$133.60	$133.60
Purchase #7	$106.50	5.257%	$112.0987	$112.10	$112.10	$112.10
7 purchase totals =	$982.92		$1,058.4605	$1,058.46	$1,058.45	$1,058.50