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	$133.28	7.184%	$142.8548	$142.85	$142.85	$142.90
Purchase #2	$84.29	8.432%	$91.3973	$91.40	$91.40	$91.40
Purchase #3	$97.39	11.371%	$108.4642	$108.46	$108.45	$108.50
Purchase #4	$219.96	6.190%	$233.5755	$233.58	$233.60	$233.60
Purchase #5	$132.96	7.412%	$142.815	$142.82	$142.80	$142.80
Purchase #6	$196.38	11.374%	$218.7163	$218.72	$218.70	$218.70
Purchase #7	$59.40	4.678%	$62.1787	$62.18	$62.20	$62.20
7 purchase totals =	$923.66		$1,000.0018	$1,000.01	$1,000.00	$1,000.10