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	$152.78	12.588%	$172.0119	$172.01	$172.00	$172.00
Purchase #2	$237.87	13.114%	$269.0643	$269.06	$269.05	$269.10
Purchase #3	$91.93	3.826%	$95.4472	$95.45	$95.45	$95.40
Purchase #4	$17.72	13.273%	$20.072	$20.07	$20.05	$20.10
Purchase #5	$54.49	9.425%	$59.6257	$59.63	$59.65	$59.60
Purchase #6	$111.87	7.222%	$119.9493	$119.95	$119.95	$119.90
Purchase #7	$23.36	7.611%	$25.1379	$25.14	$25.15	$25.10
7 purchase totals =	$690.02		$761.3083	$761.31	$761.30	$761.20