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	$162.31	7.450%	$174.4021	$174.40	$174.40	$174.40
Purchase #2	$208.94	6.482%	$222.4835	$222.48	$222.50	$222.50
Purchase #3	$153.42	7.355%	$164.704	$164.70	$164.70	$164.70
Purchase #4	$64.71	4.833%	$67.8374	$67.84	$67.85	$67.80
Purchase #5	$199.53	4.486%	$208.4809	$208.48	$208.50	$208.50
Purchase #6	$163.96	6.713%	$174.9666	$174.97	$174.95	$175.00
Purchase #7	$80.41	12.151%	$90.1806	$90.18	$90.20	$90.20
7 purchase totals =	$1,033.28		$1,103.0551	$1,103.05	$1,103.10	$1,103.10