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	$113.65	5.444%	$119.8371	$119.84	$119.85	$119.80
Purchase #2	$157.94	6.862%	$168.7778	$168.78	$168.80	$168.80
Purchase #3	$63.78	6.596%	$67.9869	$67.99	$68.00	$68.00
Purchase #4	$218.82	9.625%	$239.8814	$239.88	$239.90	$239.90
Purchase #5	$174.42	4.226%	$181.791	$181.79	$181.80	$181.80
Purchase #6	$120.47	9.344%	$131.7267	$131.73	$131.75	$131.70
Purchase #7	$80.64	12.610%	$90.8087	$90.81	$90.80	$90.80
7 purchase totals =	$929.72		$1,000.8096	$1,000.82	$1,000.90	$1,000.80