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	$108.35	7.502%	$116.4784	$116.48	$116.50	$116.50
Purchase #2	$115.37	6.298%	$122.636	$122.64	$122.65	$122.60
Purchase #3	$99.46	3.566%	$103.0067	$103.01	$103.00	$103.00
Purchase #4	$138.38	9.165%	$151.0625	$151.06	$151.05	$151.10
Purchase #5	$220.71	10.188%	$243.1959	$243.20	$243.20	$243.20
Purchase #6	$86.71	4.227%	$90.3752	$90.38	$90.40	$90.40
Purchase #7	$89.83	13.816%	$102.2409	$102.24	$102.25	$102.20
7 purchase totals =	$858.81		$928.9956	$929.01	$929.05	$929.00