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	$197.67	6.670%	$210.8546	$210.85	$210.85	$210.90
Purchase #2	$78.95	13.228%	$89.3935	$89.39	$89.40	$89.40
Purchase #3	$16.51	3.340%	$17.0614	$17.06	$17.05	$17.10
Purchase #4	$116.49	13.711%	$132.4619	$132.46	$132.45	$132.50
Purchase #5	$238.82	13.186%	$270.3108	$270.31	$270.30	$270.30
Purchase #6	$80.70	10.807%	$89.4212	$89.42	$89.40	$89.40
Purchase #7	$208.40	6.176%	$221.2708	$221.27	$221.25	$221.30
7 purchase totals =	$937.54		$1,030.7742	$1,030.76	$1,030.70	$1,030.90