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	$99.54	8.235%	$107.7371	$107.74	$107.75	$107.70
Purchase #2	$117.38	11.835%	$131.2719	$131.27	$131.25	$131.30
Purchase #3	$55.45	13.392%	$62.8759	$62.88	$62.90	$62.90
Purchase #4	$176.31	3.484%	$182.4526	$182.45	$182.45	$182.50
Purchase #5	$151.79	13.126%	$171.714	$171.71	$171.70	$171.70
Purchase #6	$168.45	8.151%	$182.1804	$182.18	$182.20	$182.20
Purchase #7	$223.67	6.643%	$238.5284	$238.53	$238.55	$238.50
7 purchase totals =	$992.59		$1,076.7603	$1,076.76	$1,076.80	$1,076.80