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	$127.47	9.834%	$140.0054	$140.01	$140.00	$140.00
Purchase #2	$11.32	3.752%	$11.7447	$11.74	$11.75	$11.70
Purchase #3	$98.37	13.350%	$111.5024	$111.50	$111.50	$111.50
Purchase #4	$93.31	3.315%	$96.4032	$96.40	$96.40	$96.40
Purchase #5	$194.90	12.452%	$219.1689	$219.17	$219.15	$219.20
Purchase #6	$55.84	11.360%	$62.1834	$62.18	$62.20	$62.20
Purchase #7	$116.68	13.547%	$132.4866	$132.49	$132.50	$132.50
7 purchase totals =	$697.89		$773.4946	$773.49	$773.50	$773.50