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	$109.36	4.804%	$114.6137	$114.61	$114.60	$114.60
Purchase #2	$17.91	8.861%	$19.497	$19.50	$19.50	$19.50
Purchase #3	$141.27	10.618%	$156.27	$156.27	$156.25	$156.30
Purchase #4	$28.96	8.457%	$31.4091	$31.41	$31.40	$31.40
Purchase #5	$181.25	10.459%	$200.2069	$200.21	$200.20	$200.20
Purchase #6	$231.68	13.242%	$262.3591	$262.36	$262.35	$262.40
Purchase #7	$189.32	3.641%	$196.2131	$196.21	$196.20	$196.20
7 purchase totals =	$899.75		$980.5689	$980.57	$980.50	$980.60