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	$205.98	7.815%	$222.0773	$222.08	$222.10	$222.10
Purchase #2	$191.78	12.827%	$216.3796	$216.38	$216.40	$216.40
Purchase #3	$124.38	4.203%	$129.6077	$129.61	$129.60	$129.60
Purchase #4	$44.95	12.572%	$50.6011	$50.60	$50.60	$50.60
Purchase #5	$111.89	10.358%	$123.4796	$123.48	$123.50	$123.50
Purchase #6	$36.80	10.592%	$40.6979	$40.70	$40.70	$40.70
Purchase #7	$156.96	9.167%	$171.3485	$171.35	$171.35	$171.30
7 purchase totals =	$872.74		$954.1917	$954.20	$954.25	$954.20