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	$219.41	5.501%	$231.4797	$231.48	$231.50	$231.50
Purchase #2	$186.57	11.661%	$208.3259	$208.33	$208.35	$208.30
Purchase #3	$131.94	12.641%	$148.6185	$148.62	$148.60	$148.60
Purchase #4	$92.48	9.298%	$101.0788	$101.08	$101.10	$101.10
Purchase #5	$50.70	4.106%	$52.7817	$52.78	$52.80	$52.80
Purchase #6	$133.87	12.322%	$150.3655	$150.37	$150.35	$150.40
Purchase #7	$114.36	7.586%	$123.0353	$123.04	$123.05	$123.00
7 purchase totals =	$929.33		$1,015.6854	$1,015.70	$1,015.75	$1,015.70