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	$120.90	11.112%	$134.3344	$134.33	$134.35	$134.30
Purchase #2	$22.86	7.380%	$24.5471	$24.55	$24.55	$24.50
Purchase #3	$215.82	7.471%	$231.9439	$231.94	$231.95	$231.90
Purchase #4	$201.96	4.125%	$210.2909	$210.29	$210.30	$210.30
Purchase #5	$158.48	13.194%	$179.3899	$179.39	$179.40	$179.40
Purchase #6	$143.35	10.414%	$158.2785	$158.28	$158.30	$158.30
Purchase #7	$132.32	11.507%	$147.5461	$147.55	$147.55	$147.50
7 purchase totals =	$995.69		$1,086.3308	$1,086.33	$1,086.40	$1,086.20