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	$150.54	11.159%	$167.3388	$167.34	$167.35	$167.30
Purchase #2	$243.98	4.850%	$255.813	$255.81	$255.80	$255.80
Purchase #3	$52.59	3.723%	$54.5479	$54.55	$54.55	$54.50
Purchase #4	$95.59	12.409%	$107.4518	$107.45	$107.45	$107.50
Purchase #5	$140.63	13.253%	$159.2677	$159.27	$159.25	$159.30
Purchase #6	$20.55	5.765%	$21.7347	$21.73	$21.75	$21.70
Purchase #7	$201.37	4.529%	$210.49	$210.49	$210.50	$210.50
7 purchase totals =	$905.25		$976.6439	$976.64	$976.65	$976.60