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	$162.72	10.346%	$179.555	$179.56	$179.55	$179.60
Purchase #2	$82.90	8.472%	$89.9233	$89.92	$89.90	$89.90
Purchase #3	$136.67	3.612%	$141.6065	$141.61	$141.60	$141.60
Purchase #4	$73.79	10.337%	$81.4177	$81.42	$81.40	$81.40
Purchase #5	$196.63	5.410%	$207.2677	$207.27	$207.25	$207.30
Purchase #6	$136.88	5.215%	$144.0183	$144.02	$144.00	$144.00
Purchase #7	$114.44	7.259%	$122.7472	$122.75	$122.75	$122.70
7 purchase totals =	$904.03		$966.5357	$966.55	$966.45	$966.50