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	$55.70	5.712%	$58.8816	$58.88	$58.90	$58.90
Purchase #2	$77.89	6.342%	$82.8298	$82.83	$82.85	$82.80
Purchase #3	$51.67	11.600%	$57.6637	$57.66	$57.65	$57.70
Purchase #4	$156.50	5.803%	$165.5817	$165.58	$165.60	$165.60
Purchase #5	$220.50	11.768%	$246.4484	$246.45	$246.45	$246.40
Purchase #6	$229.59	13.718%	$261.0852	$261.09	$261.10	$261.10
Purchase #7	$137.63	10.793%	$152.4844	$152.48	$152.50	$152.50
7 purchase totals =	$929.48		$1,024.9748	$1,024.97	$1,025.05	$1,025.00