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	$212.35	9.539%	$232.6061	$232.61	$232.60	$232.60
Purchase #2	$158.93	5.670%	$167.9413	$167.94	$167.95	$167.90
Purchase #3	$141.74	12.860%	$159.9678	$159.97	$159.95	$160.00
Purchase #4	$82.90	10.112%	$91.2828	$91.28	$91.30	$91.30
Purchase #5	$204.51	8.660%	$222.2206	$222.22	$222.20	$222.20
Purchase #6	$75.86	12.566%	$85.3926	$85.39	$85.40	$85.40
Purchase #7	$40.75	3.187%	$42.0487	$42.05	$42.05	$42.00
7 purchase totals =	$917.04		$1,001.4599	$1,001.46	$1,001.45	$1,001.40