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	$232.44	4.789%	$243.5716	$243.57	$243.55	$243.60
Purchase #2	$60.52	11.318%	$67.3697	$67.37	$67.35	$67.40
Purchase #3	$55.96	3.509%	$57.9236	$57.92	$57.90	$57.90
Purchase #4	$138.79	11.453%	$154.6856	$154.69	$154.70	$154.70
Purchase #5	$166.67	5.307%	$175.5152	$175.52	$175.50	$175.50
Purchase #6	$182.56	4.263%	$190.3425	$190.34	$190.35	$190.30
Purchase #7	$112.87	6.261%	$119.9368	$119.94	$119.95	$119.90
7 purchase totals =	$949.81		$1,009.3450	$1,009.35	$1,009.30	$1,009.30