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	$111.26	5.224%	$117.0722	$117.07	$117.05	$117.10
Purchase #2	$159.46	5.481%	$168.2	$168.20	$168.20	$168.20
Purchase #3	$106.93	5.228%	$112.5203	$112.52	$112.50	$112.50
Purchase #4	$199.74	11.709%	$223.1276	$223.13	$223.15	$223.10
Purchase #5	$106.80	6.475%	$113.7153	$113.72	$113.70	$113.70
Purchase #6	$34.83	11.490%	$38.832	$38.83	$38.85	$38.80
Purchase #7	$149.73	12.631%	$168.6424	$168.64	$168.65	$168.60
7 purchase totals =	$868.75		$942.1098	$942.11	$942.10	$942.00