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	$88.63	8.581%	$96.2353	$96.24	$96.25	$96.20
Purchase #2	$136.60	7.769%	$147.2125	$147.21	$147.20	$147.20
Purchase #3	$95.50	3.144%	$98.5025	$98.50	$98.50	$98.50
Purchase #4	$8.98	4.495%	$9.3837	$9.38	$9.40	$9.40
Purchase #5	$196.78	9.501%	$215.4761	$215.48	$215.50	$215.50
Purchase #6	$224.55	13.787%	$255.5087	$255.51	$255.50	$255.50
Purchase #7	$134.79	12.863%	$152.128	$152.13	$152.15	$152.10
7 purchase totals =	$885.83		$974.4468	$974.45	$974.50	$974.40