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	$65.40	6.807%	$69.8518	$69.85	$69.85	$69.90
Purchase #2	$213.86	8.250%	$231.5035	$231.50	$231.50	$231.50
Purchase #3	$164.74	6.346%	$175.1944	$175.19	$175.20	$175.20
Purchase #4	$168.58	8.317%	$182.6008	$182.60	$182.60	$182.60
Purchase #5	$157.34	5.440%	$165.8993	$165.90	$165.90	$165.90
Purchase #6	$161.46	6.217%	$171.498	$171.50	$171.50	$171.50
Purchase #7	$20.36	4.783%	$21.3338	$21.33	$21.35	$21.30
7 purchase totals =	$951.74		$1,017.8816	$1,017.87	$1,017.90	$1,017.90