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	$187.37	4.736%	$196.2438	$196.24	$196.25	$196.20
Purchase #2	$75.94	11.242%	$84.4772	$84.48	$84.50	$84.50
Purchase #3	$88.96	12.834%	$100.3771	$100.38	$100.40	$100.40
Purchase #4	$138.98	3.451%	$143.7762	$143.78	$143.80	$143.80
Purchase #5	$148.51	6.542%	$158.2255	$158.23	$158.25	$158.20
Purchase #6	$75.74	9.492%	$82.9292	$82.93	$82.95	$82.90
Purchase #7	$98.59	6.687%	$105.1827	$105.18	$105.20	$105.20
7 purchase totals =	$814.09		$871.2117	$871.22	$871.35	$871.20