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	$214.61	13.189%	$242.9149	$242.91	$242.90	$242.90
Purchase #2	$199.83	12.673%	$225.1545	$225.15	$225.15	$225.20
Purchase #3	$68.46	13.258%	$77.5364	$77.54	$77.55	$77.50
Purchase #4	$68.33	12.837%	$77.1015	$77.10	$77.10	$77.10
Purchase #5	$117.59	9.682%	$128.9751	$128.98	$129.00	$129.00
Purchase #6	$103.38	9.107%	$112.7948	$112.79	$112.80	$112.80
Purchase #7	$101.85	9.449%	$111.4738	$111.47	$111.45	$111.50
7 purchase totals =	$874.05		$975.9510	$975.94	$975.95	$976.00