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	$191.74	3.565%	$198.5755	$198.58	$198.60	$198.60
Purchase #2	$186.29	3.277%	$192.3947	$192.39	$192.40	$192.40
Purchase #3	$92.82	10.403%	$102.4761	$102.48	$102.50	$102.50
Purchase #4	$78.29	10.487%	$86.5003	$86.50	$86.50	$86.50
Purchase #5	$61.98	9.417%	$67.8167	$67.82	$67.80	$67.80
Purchase #6	$17.89	5.746%	$18.918	$18.92	$18.90	$18.90
Purchase #7	$226.58	6.507%	$241.3236	$241.32	$241.30	$241.30
7 purchase totals =	$855.59		$908.0049	$908.01	$908.00	$908.00