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	$142.54	10.414%	$157.3841	$157.38	$157.40	$157.40
Purchase #2	$54.50	10.855%	$60.416	$60.42	$60.40	$60.40
Purchase #3	$107.48	8.365%	$116.4707	$116.47	$116.45	$116.50
Purchase #4	$61.79	4.298%	$64.4457	$64.45	$64.45	$64.40
Purchase #5	$210.94	7.854%	$227.5072	$227.51	$227.50	$227.50
Purchase #6	$146.50	9.548%	$160.4878	$160.49	$160.50	$160.50
Purchase #7	$211.33	5.387%	$222.7143	$222.71	$222.70	$222.70
7 purchase totals =	$935.08		$1,009.4258	$1,009.43	$1,009.40	$1,009.40