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	$40.25	8.343%	$43.6081	$43.61	$43.60	$43.60
Purchase #2	$72.71	11.322%	$80.9422	$80.94	$80.95	$80.90
Purchase #3	$66.36	9.653%	$72.7657	$72.77	$72.75	$72.80
Purchase #4	$145.79	7.474%	$156.6863	$156.69	$156.70	$156.70
Purchase #5	$196.84	3.438%	$203.6074	$203.61	$203.60	$203.60
Purchase #6	$39.60	9.850%	$43.5006	$43.50	$43.50	$43.50
Purchase #7	$154.33	7.738%	$166.2721	$166.27	$166.25	$166.30
7 purchase totals =	$715.88		$767.3824	$767.39	$767.35	$767.40