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	$97.67	3.837%	$101.4176	$101.42	$101.40	$101.40
Purchase #2	$178.79	5.805%	$189.1688	$189.17	$189.15	$189.20
Purchase #3	$75.42	4.638%	$78.918	$78.92	$78.90	$78.90
Purchase #4	$241.85	8.703%	$262.8982	$262.90	$262.90	$262.90
Purchase #5	$202.79	11.526%	$226.1636	$226.16	$226.15	$226.20
Purchase #6	$96.59	13.602%	$109.7282	$109.73	$109.75	$109.70
Purchase #7	$101.58	10.694%	$112.443	$112.44	$112.45	$112.40
7 purchase totals =	$994.69		$1,080.7374	$1,080.74	$1,080.70	$1,080.70