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	$88.33	10.484%	$97.5905	$97.59	$97.60	$97.60
Purchase #2	$250.72	9.870%	$275.4661	$275.47	$275.45	$275.50
Purchase #3	$162.76	5.308%	$171.3993	$171.40	$171.40	$171.40
Purchase #4	$183.89	3.801%	$190.8797	$190.88	$190.90	$190.90
Purchase #5	$43.30	9.455%	$47.394	$47.39	$47.40	$47.40
Purchase #6	$150.70	3.847%	$156.4974	$156.50	$156.50	$156.50
Purchase #7	$207.75	4.367%	$216.8224	$216.82	$216.80	$216.80
7 purchase totals =	$1,087.45		$1,156.0494	$1,156.05	$1,156.05	$1,156.10