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	$58.67	3.792%	$60.8948	$60.89	$60.90	$60.90
Purchase #2	$175.68	11.338%	$195.5986	$195.60	$195.60	$195.60
Purchase #3	$53.32	12.255%	$59.8544	$59.85	$59.85	$59.90
Purchase #4	$170.52	12.326%	$191.5383	$191.54	$191.55	$191.50
Purchase #5	$147.62	7.664%	$158.9336	$158.93	$158.95	$158.90
Purchase #6	$156.79	11.262%	$174.4477	$174.45	$174.45	$174.40
Purchase #7	$182.57	4.172%	$190.1868	$190.19	$190.20	$190.20
7 purchase totals =	$945.17		$1,031.4542	$1,031.45	$1,031.50	$1,031.40