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	$33.58	11.836%	$37.5545	$37.55	$37.55	$37.60
Purchase #2	$187.43	4.724%	$196.2842	$196.28	$196.30	$196.30
Purchase #3	$98.90	12.483%	$111.2457	$111.25	$111.25	$111.20
Purchase #4	$189.70	6.167%	$201.3988	$201.40	$201.40	$201.40
Purchase #5	$204.76	13.471%	$232.3432	$232.34	$232.35	$232.30
Purchase #6	$233.78	12.142%	$262.1656	$262.17	$262.15	$262.20
Purchase #7	$33.61	8.493%	$36.4645	$36.46	$36.45	$36.50
7 purchase totals =	$981.76		$1,077.4565	$1,077.45	$1,077.45	$1,077.50