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	$100.27	3.113%	$103.3914	$103.39	$103.40	$103.40
Purchase #2	$250.67	10.557%	$277.1332	$277.13	$277.15	$277.10
Purchase #3	$111.65	3.120%	$115.1335	$115.13	$115.15	$115.10
Purchase #4	$90.49	13.153%	$102.3921	$102.39	$102.40	$102.40
Purchase #5	$194.57	11.539%	$217.0214	$217.02	$217.00	$217.00
Purchase #6	$118.72	11.192%	$132.0071	$132.01	$132.00	$132.00
Purchase #7	$155.32	5.785%	$164.3053	$164.31	$164.30	$164.30
7 purchase totals =	$1,021.69		$1,111.3840	$1,111.38	$1,111.40	$1,111.30