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	$62.87	9.231%	$68.6735	$68.67	$68.65	$68.70
Purchase #2	$170.90	8.178%	$184.8762	$184.88	$184.90	$184.90
Purchase #3	$244.74	10.396%	$270.1832	$270.18	$270.20	$270.20
Purchase #4	$174.92	9.409%	$191.3782	$191.38	$191.40	$191.40
Purchase #5	$164.68	8.240%	$178.2496	$178.25	$178.25	$178.20
Purchase #6	$184.37	6.788%	$196.885	$196.89	$196.90	$196.90
Purchase #7	$13.68	12.644%	$15.4097	$15.41	$15.40	$15.40
7 purchase totals =	$1,016.16		$1,105.6554	$1,105.66	$1,105.70	$1,105.70