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	$176.68	11.195%	$196.4593	$196.46	$196.45	$196.50
Purchase #2	$66.39	5.865%	$70.2838	$70.28	$70.30	$70.30
Purchase #3	$100.52	9.310%	$109.8784	$109.88	$109.90	$109.90
Purchase #4	$187.48	8.750%	$203.8845	$203.88	$203.90	$203.90
Purchase #5	$50.50	7.158%	$54.1148	$54.11	$54.10	$54.10
Purchase #6	$60.64	4.489%	$63.3621	$63.36	$63.35	$63.40
Purchase #7	$243.65	12.429%	$273.9333	$273.93	$273.95	$273.90
7 purchase totals =	$885.86		$971.9162	$971.90	$971.95	$972.00