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	$99.37	12.340%	$111.6323	$111.63	$111.65	$111.60
Purchase #2	$22.50	3.696%	$23.3316	$23.33	$23.35	$23.30
Purchase #3	$200.85	9.782%	$220.4971	$220.50	$220.50	$220.50
Purchase #4	$49.79	5.264%	$52.4109	$52.41	$52.40	$52.40
Purchase #5	$236.81	5.591%	$250.05	$250.05	$250.05	$250.10
Purchase #6	$235.28	11.380%	$262.0549	$262.05	$262.05	$262.10
Purchase #7	$237.25	13.598%	$269.5113	$269.51	$269.50	$269.50
7 purchase totals =	$1,081.85		$1,189.4881	$1,189.48	$1,189.50	$1,189.50