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	$93.72	10.849%	$103.8877	$103.89	$103.90	$103.90
Purchase #2	$27.66	3.547%	$28.6411	$28.64	$28.65	$28.60
Purchase #3	$119.90	4.871%	$125.7403	$125.74	$125.75	$125.70
Purchase #4	$85.30	5.624%	$90.0973	$90.10	$90.10	$90.10
Purchase #5	$155.38	7.129%	$166.457	$166.46	$166.45	$166.50
Purchase #6	$110.97	6.672%	$118.3739	$118.37	$118.35	$118.40
Purchase #7	$156.85	9.493%	$171.7398	$171.74	$171.75	$171.70
7 purchase totals =	$749.78		$804.9371	$804.94	$804.95	$804.90