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	$114.70	7.245%	$123.01	$123.01	$123.00	$123.00
Purchase #2	$84.80	7.799%	$91.4136	$91.41	$91.40	$91.40
Purchase #3	$57.82	6.295%	$61.4598	$61.46	$61.45	$61.50
Purchase #4	$217.98	3.381%	$225.3499	$225.35	$225.35	$225.30
Purchase #5	$43.27	9.754%	$47.4906	$47.49	$47.50	$47.50
Purchase #6	$67.94	6.204%	$72.155	$72.16	$72.15	$72.20
Purchase #7	$5.78	3.446%	$5.9792	$5.98	$6.00	$6.00
7 purchase totals =	$592.29		$626.8581	$626.86	$626.85	$626.90