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	$129.45	11.590%	$144.4533	$144.45	$144.45	$144.50
Purchase #2	$73.54	11.868%	$82.2677	$82.27	$82.25	$82.30
Purchase #3	$180.89	4.534%	$189.0916	$189.09	$189.10	$189.10
Purchase #4	$39.96	9.479%	$43.7478	$43.75	$43.75	$43.70
Purchase #5	$105.46	7.386%	$113.2493	$113.25	$113.25	$113.20
Purchase #6	$194.41	5.321%	$204.7546	$204.75	$204.75	$204.80
Purchase #7	$114.63	4.317%	$119.5786	$119.58	$119.60	$119.60
7 purchase totals =	$838.34		$897.1429	$897.14	$897.15	$897.20