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	$10.71	5.232%	$11.2703	$11.27	$11.25	$11.30
Purchase #2	$55.59	3.448%	$57.5067	$57.51	$57.50	$57.50
Purchase #3	$225.45	4.651%	$235.9357	$235.94	$235.95	$235.90
Purchase #4	$143.36	13.360%	$162.5129	$162.51	$162.50	$162.50
Purchase #5	$246.66	13.529%	$280.0306	$280.03	$280.05	$280.00
Purchase #6	$168.41	5.855%	$178.2704	$178.27	$178.25	$178.30
Purchase #7	$75.34	6.482%	$80.2235	$80.22	$80.20	$80.20
7 purchase totals =	$925.52		$1,005.7501	$1,005.75	$1,005.70	$1,005.70