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	$47.87	4.245%	$49.9021	$49.90	$49.90	$49.90
Purchase #2	$166.40	4.540%	$173.9546	$173.95	$173.95	$174.00
Purchase #3	$177.63	5.542%	$187.4743	$187.47	$187.45	$187.50
Purchase #4	$90.28	12.743%	$101.7844	$101.78	$101.80	$101.80
Purchase #5	$137.89	10.593%	$152.4967	$152.50	$152.50	$152.50
Purchase #6	$198.32	6.199%	$210.6139	$210.61	$210.60	$210.60
Purchase #7	$119.37	7.323%	$128.1115	$128.11	$128.10	$128.10
7 purchase totals =	$937.76		$1,004.3375	$1,004.32	$1,004.30	$1,004.40