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	$46.31	13.176%	$52.4118	$52.41	$52.40	$52.40
Purchase #2	$124.35	5.302%	$130.943	$130.94	$130.95	$130.90
Purchase #3	$241.98	12.848%	$273.0696	$273.07	$273.05	$273.10
Purchase #4	$201.26	10.872%	$223.141	$223.14	$223.15	$223.10
Purchase #5	$165.67	9.802%	$181.909	$181.91	$181.90	$181.90
Purchase #6	$86.70	5.522%	$91.4876	$91.49	$91.50	$91.50
Purchase #7	$117.27	12.680%	$132.1398	$132.14	$132.15	$132.10
7 purchase totals =	$983.54		$1,085.1018	$1,085.10	$1,085.10	$1,085.00