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	$245.49	8.151%	$265.4999	$265.50	$265.50	$265.50
Purchase #2	$145.33	12.437%	$163.4047	$163.40	$163.40	$163.40
Purchase #3	$51.56	9.721%	$56.5721	$56.57	$56.55	$56.60
Purchase #4	$88.90	10.804%	$98.5048	$98.50	$98.50	$98.50
Purchase #5	$129.28	11.693%	$144.3967	$144.40	$144.40	$144.40
Purchase #6	$225.96	3.484%	$233.8324	$233.83	$233.85	$233.80
Purchase #7	$131.36	11.540%	$146.5189	$146.52	$146.50	$146.50
7 purchase totals =	$1,017.88		$1,108.7295	$1,108.72	$1,108.70	$1,108.70