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	$85.56	4.256%	$89.2014	$89.20	$89.20	$89.20
Purchase #2	$166.57	9.549%	$182.4758	$182.48	$182.50	$182.50
Purchase #3	$156.96	3.161%	$161.9215	$161.92	$161.90	$161.90
Purchase #4	$80.33	13.866%	$91.4686	$91.47	$91.45	$91.50
Purchase #5	$165.74	10.863%	$183.7443	$183.74	$183.75	$183.70
Purchase #6	$202.86	7.685%	$218.4498	$218.45	$218.45	$218.40
Purchase #7	$238.81	6.816%	$255.0873	$255.09	$255.10	$255.10
7 purchase totals =	$1,096.83		$1,182.3487	$1,182.35	$1,182.35	$1,182.30