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	$215.90	4.309%	$225.2031	$225.20	$225.20	$225.20
Purchase #2	$182.52	6.573%	$194.517	$194.52	$194.50	$194.50
Purchase #3	$191.40	3.718%	$198.5163	$198.52	$198.50	$198.50
Purchase #4	$125.42	4.519%	$131.0877	$131.09	$131.10	$131.10
Purchase #5	$142.46	8.469%	$154.5249	$154.52	$154.50	$154.50
Purchase #6	$85.86	11.712%	$95.9159	$95.92	$95.90	$95.90
Purchase #7	$152.94	12.254%	$171.6813	$171.68	$171.70	$171.70
7 purchase totals =	$1,096.50		$1,171.4462	$1,171.45	$1,171.40	$1,171.40