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	$174.85	11.614%	$195.1571	$195.16	$195.15	$195.20
Purchase #2	$175.90	11.250%	$195.6888	$195.69	$195.70	$195.70
Purchase #3	$38.43	10.769%	$42.5685	$42.57	$42.55	$42.60
Purchase #4	$132.71	8.360%	$143.8046	$143.80	$143.80	$143.80
Purchase #5	$73.80	11.548%	$82.3224	$82.32	$82.30	$82.30
Purchase #6	$200.81	7.262%	$215.3928	$215.39	$215.40	$215.40
Purchase #7	$14.81	7.372%	$15.9018	$15.90	$15.90	$15.90
7 purchase totals =	$811.31		$890.8360	$890.83	$890.80	$890.90