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	$236.50	9.371%	$258.6624	$258.66	$258.65	$258.70
Purchase #2	$214.87	8.691%	$233.5444	$233.54	$233.55	$233.50
Purchase #3	$174.63	12.773%	$196.9355	$196.94	$196.95	$196.90
Purchase #4	$80.87	12.268%	$90.7911	$90.79	$90.80	$90.80
Purchase #5	$73.51	6.399%	$78.2139	$78.21	$78.20	$78.20
Purchase #6	$74.26	5.625%	$78.4371	$78.44	$78.45	$78.40
Purchase #7	$250.70	5.488%	$264.4584	$264.46	$264.45	$264.50
7 purchase totals =	$1,105.34		$1,201.0428	$1,201.04	$1,201.05	$1,201.00