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	$234.96	3.715%	$243.6888	$243.69	$243.70	$243.70
Purchase #2	$54.57	13.622%	$62.0035	$62.00	$62.00	$62.00
Purchase #3	$163.40	7.108%	$175.0145	$175.01	$175.00	$175.00
Purchase #4	$79.59	12.614%	$89.6295	$89.63	$89.65	$89.60
Purchase #5	$177.93	10.368%	$196.3778	$196.38	$196.40	$196.40
Purchase #6	$126.77	8.687%	$137.7825	$137.78	$137.80	$137.80
Purchase #7	$247.63	10.494%	$273.6163	$273.62	$273.60	$273.60
7 purchase totals =	$1,084.85		$1,178.1129	$1,178.11	$1,178.15	$1,178.10