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	$185.46	12.493%	$208.6295	$208.63	$208.65	$208.60
Purchase #2	$229.44	10.431%	$253.3729	$253.37	$253.35	$253.40
Purchase #3	$175.76	6.595%	$187.3514	$187.35	$187.35	$187.40
Purchase #4	$246.62	13.601%	$280.1628	$280.16	$280.15	$280.20
Purchase #5	$245.69	3.587%	$254.5029	$254.50	$254.50	$254.50
Purchase #6	$222.77	12.391%	$250.3734	$250.37	$250.35	$250.40
Purchase #7	$98.88	13.669%	$112.3959	$112.40	$112.40	$112.40
7 purchase totals =	$1,404.62		$1,546.7888	$1,546.78	$1,546.75	$1,546.90