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	$130.80	9.744%	$143.5452	$143.55	$143.55	$143.50
Purchase #2	$157.46	13.347%	$178.4762	$178.48	$178.50	$178.50
Purchase #3	$191.33	4.665%	$200.2555	$200.26	$200.25	$200.30
Purchase #4	$186.46	5.218%	$196.1895	$196.19	$196.20	$196.20
Purchase #5	$182.67	6.309%	$194.1947	$194.19	$194.20	$194.20
Purchase #6	$133.31	8.452%	$144.5774	$144.58	$144.60	$144.60
Purchase #7	$7.54	11.412%	$8.4005	$8.40	$8.40	$8.40
7 purchase totals =	$989.57		$1,065.6390	$1,065.65	$1,065.70	$1,065.70