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	$167.32	10.674%	$185.1797	$185.18	$185.20	$185.20
Purchase #2	$53.85	9.590%	$59.0142	$59.01	$59.00	$59.00
Purchase #3	$84.35	9.792%	$92.6096	$92.61	$92.60	$92.60
Purchase #4	$191.55	12.702%	$215.8807	$215.88	$215.90	$215.90
Purchase #5	$211.82	13.347%	$240.0916	$240.09	$240.10	$240.10
Purchase #6	$72.91	12.438%	$81.9785	$81.98	$82.00	$82.00
Purchase #7	$183.83	3.398%	$190.0765	$190.08	$190.10	$190.10
7 purchase totals =	$965.63		$1,064.8308	$1,064.83	$1,064.90	$1,064.90