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	$203.71	9.157%	$222.3637	$222.36	$222.35	$222.40
Purchase #2	$154.75	12.869%	$174.6648	$174.66	$174.65	$174.70
Purchase #3	$223.42	6.869%	$238.7667	$238.77	$238.75	$238.80
Purchase #4	$12.26	5.531%	$12.9381	$12.94	$12.95	$12.90
Purchase #5	$136.61	4.503%	$142.7615	$142.76	$142.75	$142.80
Purchase #6	$54.56	4.534%	$57.0338	$57.03	$57.05	$57.00
Purchase #7	$147.45	6.202%	$156.5948	$156.59	$156.60	$156.60
7 purchase totals =	$932.76		$1,005.1234	$1,005.11	$1,005.10	$1,005.20