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	$243.48	4.187%	$253.6745	$253.67	$253.65	$253.70
Purchase #2	$130.69	10.615%	$144.5627	$144.56	$144.55	$144.60
Purchase #3	$51.78	3.475%	$53.5794	$53.58	$53.60	$53.60
Purchase #4	$64.79	8.792%	$70.4863	$70.49	$70.50	$70.50
Purchase #5	$233.37	9.209%	$254.861	$254.86	$254.85	$254.90
Purchase #6	$162.43	3.679%	$168.4058	$168.41	$168.40	$168.40
Purchase #7	$103.61	8.408%	$112.3215	$112.32	$112.30	$112.30
7 purchase totals =	$990.15		$1,057.8912	$1,057.89	$1,057.85	$1,058.00