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	$243.95	9.661%	$267.518	$267.52	$267.50	$267.50
Purchase #2	$143.37	13.369%	$162.5371	$162.54	$162.55	$162.50
Purchase #3	$225.77	13.252%	$255.689	$255.69	$255.70	$255.70
Purchase #4	$228.94	12.538%	$257.6445	$257.64	$257.65	$257.60
Purchase #5	$53.45	3.846%	$55.5057	$55.51	$55.50	$55.50
Purchase #6	$20.45	7.234%	$21.9294	$21.93	$21.95	$21.90
Purchase #7	$168.55	9.227%	$184.1021	$184.10	$184.10	$184.10
7 purchase totals =	$1,084.48		$1,204.9258	$1,204.93	$1,204.95	$1,204.80