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	$186.57	5.175%	$196.225	$196.23	$196.25	$196.20
Purchase #2	$95.37	7.864%	$102.8699	$102.87	$102.85	$102.90
Purchase #3	$175.26	9.393%	$191.7222	$191.72	$191.70	$191.70
Purchase #4	$92.35	11.490%	$102.961	$102.96	$102.95	$103.00
Purchase #5	$53.92	10.753%	$59.718	$59.72	$59.70	$59.70
Purchase #6	$13.29	12.667%	$14.9734	$14.97	$14.95	$15.00
Purchase #7	$106.55	12.165%	$119.5118	$119.51	$119.50	$119.50
7 purchase totals =	$723.31		$787.9813	$787.98	$787.90	$788.00