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	$165.32	4.860%	$173.3546	$173.35	$173.35	$173.40
Purchase #2	$210.66	12.789%	$237.6013	$237.60	$237.60	$237.60
Purchase #3	$27.36	5.348%	$28.8232	$28.82	$28.80	$28.80
Purchase #4	$43.53	9.462%	$47.6488	$47.65	$47.65	$47.60
Purchase #5	$59.26	5.673%	$62.6218	$62.62	$62.60	$62.60
Purchase #6	$105.26	8.646%	$114.3608	$114.36	$114.35	$114.40
Purchase #7	$55.66	6.365%	$59.2028	$59.20	$59.20	$59.20
7 purchase totals =	$667.05		$723.6133	$723.60	$723.55	$723.60