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	$228.76	7.339%	$245.5487	$245.55	$245.55	$245.50
Purchase #2	$64.54	4.554%	$67.4792	$67.48	$67.50	$67.50
Purchase #3	$43.78	5.652%	$46.2544	$46.25	$46.25	$46.30
Purchase #4	$127.42	12.730%	$143.6406	$143.64	$143.65	$143.60
Purchase #5	$147.47	9.377%	$161.2983	$161.30	$161.30	$161.30
Purchase #6	$202.37	6.312%	$215.1436	$215.14	$215.15	$215.10
Purchase #7	$196.27	3.526%	$203.1905	$203.19	$203.20	$203.20
7 purchase totals =	$1,010.61		$1,082.5553	$1,082.55	$1,082.60	$1,082.50