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	$200.38	9.227%	$218.8691	$218.87	$218.85	$218.90
Purchase #2	$106.25	11.514%	$118.4836	$118.48	$118.50	$118.50
Purchase #3	$177.29	8.108%	$191.6647	$191.66	$191.65	$191.70
Purchase #4	$137.84	10.416%	$152.1974	$152.20	$152.20	$152.20
Purchase #5	$132.88	6.187%	$141.1013	$141.10	$141.10	$141.10
Purchase #6	$38.86	6.492%	$41.3828	$41.38	$41.40	$41.40
Purchase #7	$210.54	8.102%	$227.598	$227.60	$227.60	$227.60
7 purchase totals =	$1,004.04		$1,091.2969	$1,091.29	$1,091.30	$1,091.40