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	$192.74	6.378%	$205.033	$205.03	$205.05	$205.00
Purchase #2	$208.71	7.731%	$224.8454	$224.85	$224.85	$224.80
Purchase #3	$29.95	4.772%	$31.3792	$31.38	$31.40	$31.40
Purchase #4	$67.61	5.319%	$71.2062	$71.21	$71.20	$71.20
Purchase #5	$158.71	5.614%	$167.62	$167.62	$167.60	$167.60
Purchase #6	$233.77	9.279%	$255.4615	$255.46	$255.45	$255.50
Purchase #7	$116.35	7.756%	$125.3741	$125.37	$125.35	$125.40
7 purchase totals =	$1,007.84		$1,080.9194	$1,080.92	$1,080.90	$1,080.90