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	$80.56	3.452%	$83.3409	$83.34	$83.35	$83.30
Purchase #2	$166.55	3.731%	$172.764	$172.76	$172.75	$172.80
Purchase #3	$65.64	12.107%	$73.587	$73.59	$73.60	$73.60
Purchase #4	$138.60	4.411%	$144.7136	$144.71	$144.70	$144.70
Purchase #5	$176.85	11.294%	$196.8234	$196.82	$196.80	$196.80
Purchase #6	$133.87	5.332%	$141.0079	$141.01	$141.00	$141.00
Purchase #7	$179.27	11.770%	$200.3701	$200.37	$200.35	$200.40
7 purchase totals =	$941.34		$1,012.6069	$1,012.60	$1,012.55	$1,012.60